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
diff --git a/jeepyb/gerritdb.py b/jeepyb/gerritdb.py
index 767991f..3f5db66 100644
--- a/jeepyb/gerritdb.py
+++ b/jeepyb/gerritdb.py
@@ -52,7 +52,7 @@
         DB_PASS = secure_config.get("database", "password")
         DB_DB = gerrit_config.get("database", "database")
 
-        if DB_TYPE == "MYSQL":
+        if DB_TYPE.upper() == "MYSQL":
             import MySQLdb
             db_connection = MySQLdb.connect(
                 host=DB_HOST, user=DB_USER, passwd=DB_PASS, db=DB_DB)