Fix in database discrimination

jeepyb is comparing the config setting with
MYSQL. However, it's possible that configuration is
not set on capital letters, and that is causing gerrit
configures with real mysql to fallback into the postgres
case.

Just capitalize the config setting to safely compare
with MYSQL value.

Change-Id: I5c5b920da14275d45dc1d394ca8c569709f9ab41
1 file changed