Enable the NSTP QUIC connection option in fieldtrial_testing_config.json

TBR=asvitkine@chromium.org

Bug: 862555
Change-Id: I87b37b6c2ebfd27d86e3116693dd71f18e608aaa
Reviewed-on: https://chromium-review.googlesource.com/1147513Reviewed-by: Ryan Hamilton <rch@chromium.org>
Commit-Queue: Ryan Hamilton <rch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577420}

testing/variations/fieldtrial_testing_config.json

@@ -3222,7 +3222,10 @@
             ],
             "experiments": [
                 {
-                    "name": "Enabled"
+                    "name": "Enabled",
+                    "params": {
+                        "connection_options": "NSTP"
+                    }
                 }
             ]
         }