[WFLY-1911] / [WFLY-490] Additional checks on if a username has been specified in advance so when used in scripted mode local authentication will be automatically disabled if a username has been supplied.
[WFLY-1911] Also a minor update to the testsuite.  When these tests were first written it was mandatory that a user was defined before the server could be accessed, as a result a dummy test suite user was added for testing.  However once the local authentication mechanism was added these users were no longer needed.

The tests however are attempting to connect to the server using an invalid username/password combination - this is now removed.