Fix unit test checking Gerrit plugin version

Review Request #1159 — Created April 18, 2018 and submitted — Latest diff uploaded

Review Board
The unit test that was checking for a failed plugin compatability
used hardcoded version string of 0.1.0, instead of the actual required
version. This didn't get caught during the plugin version bump that
happened when we released the gerrit plugin but has now been rectified.

The error message has also been improved to include the original version
string we receive instead of our parsed tuple.

Testing Done:
Ran unit tests.

Reviewed at