wsrep-patch uses same connection name for constructing Master_info
objects. As a result all existing wsrep Master_info objects refer
to same rpl_filter object. This could lead to race when multiple
threads try to delete/destruct Master_info object, as they would
all try to delete the same relay_log object.

Fixed by adding a check in Master_info's destructor to not free
the "wsrep" rpl_filter, so that its reused by current & subsequent
wsrep threads and later reclaimed by free_all_rpl_filters() during
server shutdown.