app_queue: Fix CLI "queue remove member" queue_log entry.

The queue_log entry resulting from CLI "queue remove member" when
log_membername_as_agent is enabled is wrong.  It always uses the interface
name instead of the member name in the queue_log entry.

* Get the queue member before removing it from the queue so the member
name is available for the queue_log entry.

(closes issue ASTERISK-21826)
Reported by: Oscar Esteve
Patches:
      fix_membername.diff (license #6505) patch uploaded by Oscar Esteve
         (modified to fix potential ref leak)


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/11@401433 f38db490-d61c-443f-a65b-d21fe96a405b