In domain ID based filtering, a flag is used to filter-out
the events that belong to a particular domain. This flag gets
set when IO thread receives a GTID_EVENT for the domain on
filter list and its reset at the last event in the GTID group.
The resetting, however, was wrongly done before the decision to
write/filter the event from relay log is made. As a result, the
last event in the group will always pass through the filter.
Fixed by deferring the reset logic. Also added a test case.