There seems to be a bug in Galera that causes
TASK [mariadb : Check MariaDB service WSREP sync status]
to fail.
One (in case of 3-node cluster) or more (possible with
more-than-3-node clusters) nodes may "lose the race" and get stuck
in the "initialized" state of WSREP.
This is entirely random as is the case with most race issues.
MariaDB service restart on that node will fix the situation but
it's unwieldy.
The above may happen because Kolla Ansible starts and waits for
all new nodes at once.
This did not bother the old galera (galera 3) which figured out
the ordering for itself and let each node join the cluster properly.
The proposed workaround is to start and wait for nodes serially.
Change-Id: I449d4c2073d4e3953e9f09725577d2e1c9d563c9
Closes-Bug: #1947485
(cherry picked from commit c94cc4a61a)
be6fd7b7df