Extend AuthRealmIT with empty realms, full get test case
SecurityService pays attention to configured realm.

This is used when digest passwords are computed.

Change default realm to SQLLayer to match what SecurityService use to
think it always was.
Fix epxected when using default
merge nathanlws: Fix HTTP digest authentication

Merge pull request #1533 from nathanlws/sql-layer/fix-digest-auth
https://github.com/FoundationDB/sql-layer/pull/1533