Update src/ZfcUser/Authentication/Adapter/Db.php

Fix for issue #198.

The used constant was not defined in the AuthenticationResult so I changed an uncategorized error.
Merge pull request #201 from hikaru-shindo/patch-1

Fix error because of undefined class constant in src/ZfcUser/Authentication/Adapter/Db.php
Merge branch 'master' of github.com:ZF-Commons/ZfcUser