Strengthen account tests

This fell out of Peter Portante's "acctcont-api" branch and seems
obviously good. Apparently one of these would've triggered while
doing the Pluggable Backend work.

Now, why commit this separately while simultaneously working on
a big unified Backend Patch? Because posting them separately
proves that the test changes worked on the old code.

Change-Id: I9ca6ad45fb255f5c0a177a93b93c1acc68da5bbe
Merge "Strengthen account tests"