Postpush fix due to problem with ha_reset_logs() being called while
holding the global read lock, thus preventing handlerton plugins to
modify their internal state tables.

Fix by unlocking the global read lock before informing handlerton
plugins using the binlog_transmit after_reset_master callback. Thus
allowing handlerton plugins to get notified by sucessful RESET MASTER
without the global read lock held.

Change-Id: I89e9675234f0e8582772accc3380a6a7803a6372