Kolla environment currently uses haproxy
to fullfill HA in mariadb. This patch
is switching haproxy to proxysql if enabled.

This patch is also replacing mariadb's user
'haproxy' with user 'monitor'. This replacement
has two reasons:
  - Use better name to "monitor" galera claster
    as there are two services using this user
    (HAProxy, ProxySQL)
  - Set password for monitor user as it's
    always better to use password then not use.
    Previous haproxy user didn't use password
    as it was historically not possible with
    haproxy and mariadb-clustercheck wasn't
    implemented.

Depends-On: https://review.opendev.org/c/openstack/kolla/+/769385
Depends-On: https://review.opendev.org/c/openstack/kolla/+/765781
Depends-On: https://review.opendev.org/c/openstack/kolla/+/850656

Change-Id: I0edae33d982c2e3f3b5f34b3d5ad07a431162844