apps/app_confbridge: Ensure 'normal' users hear message when last marked leaves

When r428077 was made for ASTERISK-24522, it failed to take into account users
who are neither wait_marked nor end_marked. These users are *also* supposed to
hear the 'leader has left the conference' message. Granted, this behaviour is
a bit odd; however, that is how it used to work... and behaviour changes are
not good.

This patch ensures that if there are any 'normal' users present when the last
marked user leaves the conference, the message will still be played to them.

Note that this regression was caught by the Asterisk Test Suite's
confbridge_nominal test, which has a quirky combination of users.


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/11@428113 f38db490-d61c-443f-a65b-d21fe96a405b
chan_sip: Fix theoretical leak of p->refer.

If transmit_refer is called when p->refer is already allocated,
it leaks the previous allocation.  Updated code to always free
previous allocation during a new allocation.  Also instead of
checking if we have a previous allocation, always create a
clean record.

ASTERISK-15242 #close
Reported by: David Woolley
Review: https://reviewboard.asterisk.org/r/4160/


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/11@428117 f38db490-d61c-443f-a65b-d21fe96a405b