google: fix nomenclature feedback and changed time.Now implementation to allow for testing for time in unit tests. The unit tests will not pass at the moment; awaiting feedback on whether to use a test credential source or rely on a separate one.

Change-Id: I20605fa161911f325ab41fc345436d08ed17ed5e

google/internal/externalaccount/filecredsource_test.go

@@ -50,7 +50,7 @@ func TestRetrieveFileSubjectToken(t *testing.T) {
 		tfc := testFileConfig
 		tfc.CredentialSource = test.cs
 
-		out, err := test.cs.instance().retrieveSubjectToken(&tfc)
+		out, err := tfc.parse().retrieveSubjectToken(&tfc)
 		if err != nil {
 			t.Errorf("Method retrieveSubjectToken for type fileCredentialSource in test %v failed; %e", test.name, err)
 		}