Clean-up mocking constructs a little bit.
Implement and test NSURLConnectionDelegate:connectionShouldUseCredentialStorage
Implement and test NSURLConnectionDelegate:willSendRequestForAuthenticationChallenge.
Implement and test NSURLConnectionDelegate:canAuthenticateAgainstProtectionSpace
Implement and test NSURLConnectionDelegate:connection:didReceiveAuthenticationChallenge:
Implement and test NSURLConnectionDelegate:connection:didCancelAuthenticationChallenge: