Disable net_unittest on Fuchsia bots

net_unittests always fail because they run slowly under qemu

Change-Id: Ief04c1ba39b5a507f0583fd7e31f4ff09492404c
Bug: 745094, 738275
Reviewed-on: https://chromium-review.googlesource.com/580048Reviewed-by: Wez <wez@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#488400}

testing/buildbot/chromium.fyi.json

@@ -10030,7 +10030,8 @@
   "Fuchsia": {
     "additional_compile_targets": [
       "gl_unittests",
-      "media_unittests"
+      "media_unittests",
+      "net_unittests"
     ],
     "gtest_tests": [
       {
@@ -10093,15 +10094,6 @@
         },
         "test": "mojo_system_unittests"
       },
-      {
-        "args": [
-          "--test-launcher-filter-file=../../testing/buildbot/filters/fuchsia.net_unittests.filter"
-        ],
-        "swarming": {
-          "can_use_on_swarming_builders": false
-        },
-        "test": "net_unittests"
-      },
       {
         "swarming": {
           "can_use_on_swarming_builders": false
@@ -10122,7 +10114,8 @@
   "Fuchsia (dbg)": {
     "additional_compile_targets": [
       "gl_unittests",
-      "media_unittests"
+      "media_unittests",
+      "net_unittests"
     ],
     "gtest_tests": [
       {
@@ -10185,15 +10178,6 @@
         },
         "test": "mojo_system_unittests"
       },
-      {
-        "args": [
-          "--test-launcher-filter-file=../../testing/buildbot/filters/fuchsia.net_unittests.filter"
-        ],
-        "swarming": {
-          "can_use_on_swarming_builders": false
-        },
-        "test": "net_unittests"
-      },
       {
         "swarming": {
           "can_use_on_swarming_builders": false