Rework slave config for first mysql master

There were instances where the first MySQL master would get its slave
config reset back to the initial configuration if the the chef runs and
completed at least once, replication were to break on the first master
node, and then chef were to run again.  When broken replication would be
reset to binlog 000001 and everything is broken horribly.

This was first reported by @JCallicoat in
https://github.com/rcbops/chef-cookbooks/issues/764.

This fix changes the checks for the first master to node to only change
the slave configuration setup when the slave is not running (i.e.
Slave_SQL_Running is not YES) AND the MAster_User is not repl.  This is
safe as we hard code the repl username.  If this changes in the future
then we have to change it here but that is in the future.