windows/svc: use separate (and more descriptive) service names in tests

Notably, the DisplayName field was set to the same thing in both
sys.TestExample and mrg.TestMyService, which may explain the collision
reported in golang/go#59298.

Moreover, the adjective ”my” conveys no information whatsoever — we
shouldn't use it in tests or examples.

Also skip the tests that install services if GO_BUILDER_NAME is not
set, to reduce the likelihood of 'go test all' in a user's working
directory being mistaken for a malicious or compromised program.

Fixes golang/go#59298.

Change-Id: Ib00bf7400bfaa34e1a1d49125c43b97019b53c82
Reviewed-on: https://go-review.googlesource.com/c/sys/+/481015
Reviewed-by: Carlos Amedee <carlos@golang.org>
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Bryan Mills <bcmills@google.com>

windows/svc/mgr/mgr_test.go

@@ -227,25 +227,26 @@ func remove(t *testing.T, s *mgr.Service) {
 }
 
 func TestMyService(t *testing.T) {
+	if os.Getenv("GO_BUILDER_NAME") == "" {
+		// Don't install services on arbitrary users' machines.
+		t.Skip("skipping test that modifies system services: GO_BUILDER_NAME not set")
+	}
 	if testing.Short() {
-		t.Skip("skipping test in short mode - it modifies system services")
+		t.Skip("skipping test in short mode that modifies system services")
 	}
 
-	const name = "mymgrservice"
+	const name = "mgrtestservice"
 
 	m, err := mgr.Connect()
 	if err != nil {
-		if errno, ok := err.(syscall.Errno); ok && errno == syscall.ERROR_ACCESS_DENIED {
-			t.Skip("Skipping test: we don't have rights to manage services.")
-		}
 		t.Fatalf("SCM connection failed: %s", err)
 	}
 	defer m.Disconnect()
 
 	c := mgr.Config{
 		StartType:    mgr.StartDisabled,
-		DisplayName:  "my service",
-		Description:  "my service is just a test",
+		DisplayName:  "x-sys mgr test service",
+		Description:  "x-sys mgr test service is just a test",
 		Dependencies: []string{"LanmanServer", "W32Time"},
 	}
 
@@ -288,14 +289,14 @@ func TestMyService(t *testing.T) {
 	if err != nil {
 		t.Fatalf("ListServices failed: %v", err)
 	}
-	var myserviceIsInstalled bool
+	var serviceIsInstalled bool
 	for _, sn := range svcnames {
 		if sn == name {
-			myserviceIsInstalled = true
+			serviceIsInstalled = true
 			break
 		}
 	}
-	if !myserviceIsInstalled {
+	if !serviceIsInstalled {
 		t.Errorf("ListServices failed to find %q service", name)
 	}