When a tripleo major upgrade or FFU causes an update or mariadb
to a new major version (e.g. 10.1 -> 10.3), some internal DB
tables must be upgraded (myisam tables), and sometimes the
existing user tables may be migrated to new mariadb defaults.
Move the db-specific upgrade steps into a dedicated script and
make sure that it is called at the right time while upgrading
the undercloud and/or the overcloud.
Closes-Bug: #1913438
Change-Id: I92353622994b28c895d95bdcbe348a73b6c6bb99
712cfcc71b