Dump and restore galera db during major upgrades

When the overcloud is upgraded we do a yum update of the packages.
This step might introduce a newer galera version. In such a situation
we need to dump the db and restore it. The high-level workflow should
be the following:
1) During the main upgrade step, before shutting down the cluster
   we need to dump the db
2) We upgrade the packages
3) We briefly start mysql on a single node while making sure that
   /root/.my.cnf is briefly moved out of the way (because it contains
   a password) and import the data. After the import we shutdown this
   mysql instance
4) We let the cluster start up normally

The above steps will take place in the following scenarios.
Given a locally installed mariadb version X.Y.Z and release R,
we will dump and restore the DB under the following conditions:
A) MySqlMajorUpgrade template parameter is set to 'auto' and
   the upgraded package differs in X, Y *or* Z. We basically don't
   dump automatically if the release field changes.

B) MySqlMajorUpgrade template parameter is set to 'yes'

When MySqlMajorUpgrade is set to 'no', no dumping will be performed.
Note that this will give a non functional upgrade if a major mariadb
upgrade is taking place.

Partial-Bug: #1587449

Co-Author: Damien Ciabrin <dciabrin@redhat.com>
Co-Author: Mike Bayer <mbayer@redhat.com>

Depends-On: I8cb4cb3193e6b823aad48ad7dbbbb227364d2a58
Depends-On: I38dcacfabc44539aab1f7da85168fe44a1b43a51

Change-Id: I374628547aed091129d0deaa29764bfc998d76ea

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