Make sure DBLoadBalancerFactory service is not disabled

After b873e929, when the CLI installation failed, the script will throw
a ServiceDisabledException.
This is because the installer disables DBLoadBalancerFactory service
during instantiation and throws the exception because the installation
failed to restore the service.
So I check if the service is enabled before try commit
the master changes.

Bug: T229601
Change-Id: Ia7589d14ee55bcb03a64856b6dd2c81d8bda783c
(cherry picked from commit eadde762b03ed94c687788ed3e0d9c65e5046fb2)