Fix galera service enabling condition

We need to be sure that enabled param is defined and set to True
during a state applying.

Change-Id: I19cd4c834f254d76d6b521d983d05b227c048065

galera/master.sls

@@ -1,5 +1,5 @@
 {%- from "galera/map.jinja" import master with context %}
-{%- if master.enabled %}
+{%- if master.get('enabled', False) %}
 
 {%- if grains.os_family == 'RedHat' %}
 xtrabackup_repo:

galera/slave.sls

@@ -1,5 +1,5 @@
 {%- from "galera/map.jinja" import slave with context %}
-{%- if slave.enabled %}
+{%- if slave.get('enabled', False) %}
 
 {%- if grains.os_family == 'RedHat' %}
 xtrabackup_repo: