test: add unit test to confirm absence of pageToken param in listBuckets request, which causes the 1000+ buckets infinite pagination loop

Author: eliekozah

google/cloud/storage/internal/rest/stub_test.cc

@@ -203,7 +203,7 @@ TEST(RestStubTest, ListBucketsIncludesPageTokenWhenPresentInRequest) {
   EXPECT_CALL(*mock,
               Get(ExpectedContext(),
                   ResultOf(
-                      "request parameters contain expected pageToken",
+                      "request parameters contain 'pageToken'",
                       [](RestRequest const& r) { return r.parameters(); },
                       Contains(Pair("pageToken", expected_token)))))
       .WillOnce(Return(PermanentError()));