Fix interpretation of PRIREDIRECTIONREASON set by chan_sip.

Fix interpretation of PRIREDIRECTIONREASON set by chan_sip.

This commit is the simplest way to solve a problem that has already been solved
in trunk with the "COLP/CONP and Redirecting party information into Asterisk"
commit. In trunk the redirection reason is translated into a generic redirect
reason. I would have had to do the same fix except chan_sip never reads
PRIREDIRECTREASON. So both chan_dahdi and chan_h323 have been modified to
interpret the one different redirect reason of "no-answer" properly and set the
ISDN reason code 2 of "no reply".

(closes issue #15033)
Reported by: steinwej

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.6.0@223404 65c4cc65-6c06-0410-ace0-fbb531ad65f3