Add command line option to check for errant transaction

[LaurentKol]

This errant transactions check is only performed if --check_for_errant_transactions is present on masterha_master_switch command line, default behavior is unchanged.

If errant transactions are found, switch-over is aborted during Phase 1 (Configuration Check Phase) and a fix is suggested using mysqlslavetrx.

This is to prevent switch-over to get stuck after the CHANGE MASTER statement with replication error 1236.