Restart container until mariadb is available

Fix a race condition between MariaDB service start and Keystone.

Change-Id: I31384204eca9c7201eb102ec0359b390e88b96ba

docker/keystone/start.sh

@@ -1,5 +1,10 @@
 #!/bin/bash
 
+# Exit the container if MariaDB is not yet up - then depend on kube to restart
+if [ -z "$MARIADBMASTER_PORT_3306_TCP_PORT" ]; then
+        exit 1
+fi
+
 : ${KEYSTONE_ADMIN_PASSWORD:=kolla}
 : ${ADMIN_TENANT_NAME:=admin}