Repair mysql root password configuration

I had to move mysql login and password to /etc/my.cnf
because mysql client could not get passsword from
~.my.cnf when ran by Puppet for some reason.

There is also a separate class mysql::password to
create this file for both plain mysql setup and Galera

Change-Id: I9a9f2a2f479ee7c4b9457329856eabffb1d2b169
Closes-bug: 1297848