verify we're running within GitHub CI

Signed-off-by: Shlomi Noach <[email protected]>

go/test/endtoend/onlineddl/vrepl_stress/onlineddl_vrepl_mini_stress_test.go

@@ -161,9 +161,9 @@ func nextOpOrder() int64 {
 }
 
 func TestInitialSetup(t *testing.T) {
-	repo, _ := os.LookupEnv("GITHUB_REPOSITORY")
+	repo, ok := os.LookupEnv("GITHUB_REPOSITORY") // `ok` tells us the env variable exists, hence that we are running in GitHub CI.
 	t.Logf("==== repo=%v", repo)
-	if repo != "vitessio/vitess" {
+	if ok && repo != "vitessio/vitess" {
 		// `vitessio/vitess` repository enjoys faster runners. Otherwise, GitHub CI has much slower runners
 		// and we have to reduce the workload
 		maxConcurrency = maxConcurrency / 2