Allow a single-node MariaDB cluster to restart properly

With the implementation of https://review.openstack.org/382683 a single
MariaDB node has no peers configured, so there's no need to bootstrap
the cluster on restart.

This patch removes the condition in the handler which previously was
needed to handle the re-bootstrap during a single node cluster service
restart.

Closes-Bug: #1595143
Closes-Bug: #1639900
Related-Bug: #1624327
Change-Id: I599bbf0efa4e3d5abdf6d95c95d7983c464b3ae5

handlers/main.yml

@@ -24,7 +24,7 @@
     state: restarted
     sleep: 2
     pattern: mysql
-    arguments: "{{ (not galera_existing_cluster | bool and inventory_hostname == galera_server_bootstrap_node) or (galera_cluster_members | length == 1) | ternary('--wsrep-new-cluster', '') }}"
+    arguments: "{{ (not galera_existing_cluster | bool and inventory_hostname == galera_server_bootstrap_node) | ternary('--wsrep-new-cluster', '') }}"
   environment:
     MYSQLD_STARTUP_TIMEOUT: 180
   when:
@@ -51,7 +51,7 @@
     state: restarted
     sleep: 2
     pattern: mysql
-    arguments: "{{ (not galera_existing_cluster | bool and inventory_hostname == galera_server_bootstrap_node) or (galera_cluster_members | length == 1) | ternary('--wsrep-new-cluster', '') }}"
+    arguments: "{{ (not galera_existing_cluster | bool and inventory_hostname == galera_server_bootstrap_node) | ternary('--wsrep-new-cluster', '') }}"
   environment:
     MYSQLD_STARTUP_TIMEOUT: 180
   register: galera_restart_fall_back