Cleanup some flags on DAHDI PRI channel hangup.

*  Cleanup some flags on DAHDI PRI channel hangup. (sig_pri split)
*  Make sure the outgoing flag is cleared if a new channel fails to get
created for outgoing calls.
*  Remove some unused flags since sig_pri was split.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@226648 65c4cc65-6c06-0410-ace0-fbb531ad65f3