Added general_log to ansible/roles/mariadb/templates/galera.cnf.j2
to improve mariadb logging.
This will be helpful to debug mariadb issues especially when
mariadb is scaled.
Test results of this patch set are at:
http://paste.openstack.org/show/492852/
Change-Id: I80438d1bbdd1ed2a1f47489c6f9c45b8107340a0
Closes-Bug: #1563668