when a PRI disconnect is received depending on which cause code was received.
(issue #9588, original patch by softins, updated patch from jtexter3, and some
additional feedback from mhardeman)
git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.2@70396 65c4cc65-6c06-0410-ace0-fbb531ad65f3