Merge pull request #3177 from stintel/mysql56-compat

Fix MySQL 5.6 compatibility

database/mysql_user

@@ -157,6 +157,7 @@ def user_mod(cursor, user, host, password, new_priv):
         # the new specification, then revoke all privileges on it.
         for db_table, priv in curr_priv.iteritems():
             if db_table not in new_priv:
+                if user != "root" and "PROXY" not in priv:
                     privileges_revoke(cursor, user,host,db_table)
                     changed = True