Extract functionality common to TestingModule/Singleton

Bug: 182885307
Test: m nothing
Change-Id: Ib7c96b34512ad2a190a24c9dd07ea259d1378b44
diff --git a/android/namespace_test.go b/android/namespace_test.go
index dea287d..604b356 100644
--- a/android/namespace_test.go
+++ b/android/namespace_test.go
@@ -697,7 +697,7 @@
 		testModule, ok := candidate.(*testModule)
 		if ok {
 			if testModule.properties.Id == id {
-				module = TestingModule{testModule}
+				module = newTestingModule(testModule)
 			}
 		}
 	}