chan_sip: Remove excess ref of realtime peer before sip_poke_peer.

The peer is referenced at the end of sip_poke_peer, it should not get
an extra ref before the call to sip_poke_peer. This fixes a memory
leak.

ASTERISK-22945 #close
Reported by: ibercom
Tested by: Yuriy Gorlichenko
Patches:
  asterisk11.patch uploaded by ibercom (License #6599)

Review: https://reviewboard.asterisk.org/r/4031/
........

Merged revisions 424176 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/11@424177 f38db490-d61c-443f-a65b-d21fe96a405b
chan_sip: Simplify some unref code by removing unlink_peer_from_tables.

ASTERISK-22945 #related
Reported by: ibercom
Patches:
  asterisk11-chan_sip-simplifies.patch uploaded by ibercom (License #6599)
........

Merged revisions 424181 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/11@424182 f38db490-d61c-443f-a65b-d21fe96a405b