MHA should support RESET SLAVE ALL in MySQL 5.5.16+

[yoshinorim]

Originally reported from Joffrey Michaie -- Thanks!

Starting with MySQL 5.5, reset slave does not loose the replication user and replication password, it just removes the replication position.
As you can imagine this is really dangerous, if the end-user does a "start slave" on the new master, this can be a disaster !

The behavior was changed in MySQL 5.1 :
http://dev.mysql.com/doc/refman/5.5/en/reset-slave.html

Starting from MySQL 5.5.16, RESET SLAVE ALL was introduced. MHA should be aware of this command.

[yoshinorim]

Fix: 4cee0be

[yoshinorim]

5.0 and 5.1 fix: d64c44f