res_pjsip_session: Fix race condition where redirecting information may not be set.

Since the PJSIP INVITE session module is invoked before any session supplements it was
possible for it to handle a redirect before the res_pjsip_diversion module interpreted
and set redirecting information on the channel. This would cause the redirecting
information to get lost.

This patch ensures that session supplements are *always* invoked before a redirect occurs
by explicitly calling them in the redirect handler.

Review: https://reviewboard.asterisk.org/r/3850/
........

Merged revisions 419764 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@419766 65c4cc65-6c06-0410-ace0-fbb531ad65f3