Don't set mastername property when setting builder_group property.

Bug: 1109276
Change-Id: I907d30149f06355e35a372127064ef01d2b2c87a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2366670
Auto-Submit: Garrett Beaty <gbeaty@chromium.org>
Reviewed-by: Stephen Martinis <martiniss@chromium.org>
Commit-Queue: Stephen Martinis <martiniss@chromium.org>
Cr-Commit-Position: refs/heads/master@{#800265}

infra/config/generated/cr-buildbucket.cfg

@@ -2810,7 +2810,7 @@ buckets {
         cipd_version: "refs/heads/master"
         cmd: "recipes"
       }
-      properties: "{\"$build/chromium_tests\":{\"bucketed_triggers\":true},\"$build/goma\":{\"enable_ats\":true,\"rpc_extra_params\":\"?prod\",\"server_host\":\"goma.chromium.org\"},\"$kitchen\":{\"devshell\":true,\"git_auth\":true},\"builder_group\":\"chromium.gpu\",\"mastername\":\"chromium.gpu\",\"recipe\":\"chromium\"}"
+      properties: "{\"$build/chromium_tests\":{\"bucketed_triggers\":true},\"$build/goma\":{\"enable_ats\":true,\"rpc_extra_params\":\"?prod\",\"server_host\":\"goma.chromium.org\"},\"$kitchen\":{\"devshell\":true,\"git_auth\":true},\"builder_group\":\"chromium.gpu\",\"recipe\":\"chromium\"}"
       execution_timeout_secs: 10800
       build_numbers: YES
       service_account: "chromium-ci-builder@chops-service-accounts.iam.gserviceaccount.com"
@@ -3470,7 +3470,7 @@ buckets {
         cipd_version: "refs/heads/master"
         cmd: "recipes"
       }
-      properties: "{\"$build/chromium_tests\":{\"bucketed_triggers\":true},\"$build/goma\":{\"enable_ats\":true,\"jobs\":500,\"rpc_extra_params\":\"?prod\",\"server_host\":\"goma.chromium.org\"},\"$kitchen\":{\"devshell\":true,\"git_auth\":true},\"builder_group\":\"chromium.linux\",\"mastername\":\"chromium.linux\",\"recipe\":\"chromium\"}"
+      properties: "{\"$build/chromium_tests\":{\"bucketed_triggers\":true},\"$build/goma\":{\"enable_ats\":true,\"jobs\":500,\"rpc_extra_params\":\"?prod\",\"server_host\":\"goma.chromium.org\"},\"$kitchen\":{\"devshell\":true,\"git_auth\":true},\"builder_group\":\"chromium.linux\",\"recipe\":\"chromium\"}"
       execution_timeout_secs: 10800
       build_numbers: YES
       service_account: "chromium-ci-builder@chops-service-accounts.iam.gserviceaccount.com"
@@ -4311,7 +4311,7 @@ buckets {
         cipd_version: "refs/heads/master"
         cmd: "recipes"
       }
-      properties: "{\"$build/chromium_tests\":{\"bucketed_triggers\":true},\"$build/goma\":{\"enable_ats\":true,\"rpc_extra_params\":\"?prod\",\"server_host\":\"goma.chromium.org\"},\"$kitchen\":{\"devshell\":true,\"git_auth\":true},\"builder_group\":\"chromium.gpu\",\"mastername\":\"chromium.gpu\",\"recipe\":\"chromium\"}"
+      properties: "{\"$build/chromium_tests\":{\"bucketed_triggers\":true},\"$build/goma\":{\"enable_ats\":true,\"rpc_extra_params\":\"?prod\",\"server_host\":\"goma.chromium.org\"},\"$kitchen\":{\"devshell\":true,\"git_auth\":true},\"builder_group\":\"chromium.gpu\",\"recipe\":\"chromium\"}"
       execution_timeout_secs: 10800
       build_numbers: YES
       service_account: "chromium-ci-builder@chops-service-accounts.iam.gserviceaccount.com"
@@ -4398,7 +4398,7 @@ buckets {
         cipd_version: "refs/heads/master"
         cmd: "recipes"
       }
-      properties: "{\"$build/chromium_tests\":{\"bucketed_triggers\":true},\"$build/goma\":{\"jobs\":500},\"$kitchen\":{\"devshell\":true,\"git_auth\":true},\"builder_group\":\"chromium.linux\",\"mastername\":\"chromium.linux\",\"recipe\":\"chromium\"}"
+      properties: "{\"$build/chromium_tests\":{\"bucketed_triggers\":true},\"$build/goma\":{\"jobs\":500},\"$kitchen\":{\"devshell\":true,\"git_auth\":true},\"builder_group\":\"chromium.linux\",\"recipe\":\"chromium\"}"
       execution_timeout_secs: 10800
       build_numbers: YES
       service_account: "chromium-ci-builder@chops-service-accounts.iam.gserviceaccount.com"
@@ -25521,7 +25521,7 @@ buckets {
         cipd_version: "refs/heads/master"
         cmd: "recipes"
       }
-      properties: "{\"$build/code_coverage\":{\"use_clang_coverage\":true},\"$build/goma\":{\"enable_ats\":true,\"jobs\":150,\"rpc_extra_params\":\"?prod\",\"server_host\":\"goma.chromium.org\"},\"$kitchen\":{\"devshell\":true,\"git_auth\":true},\"builder_group\":\"tryserver.chromium.linux\",\"mastername\":\"tryserver.chromium.linux\",\"recipe\":\"chromium_trybot\"}"
+      properties: "{\"$build/code_coverage\":{\"use_clang_coverage\":true},\"$build/goma\":{\"enable_ats\":true,\"jobs\":150,\"rpc_extra_params\":\"?prod\",\"server_host\":\"goma.chromium.org\"},\"$kitchen\":{\"devshell\":true,\"git_auth\":true},\"builder_group\":\"tryserver.chromium.linux\",\"recipe\":\"chromium_trybot\"}"
       execution_timeout_secs: 14400
       expiration_secs: 7200
       caches {

infra/config/lib/builders.star

@@ -470,7 +470,7 @@ def builder(
 
     if builder_group != None:
         properties["builder_group"] = builder_group
-    if mastername != None:
+    elif mastername != None:
         properties["mastername"] = mastername
 
     pool = defaults.get_value("pool", pool)