app_dial: Honor the 'c' flag when the calling party hangs up

Apparently this feature became broken in 11, probably as a result
of the Hangup Cause project.

(closes issue ASTERISK-21113)
Reprted by: Heiko Wundram
Patches:
	app_dial.patch uploaded by Heiko Wundram (license 5822)


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@381880 65c4cc65-6c06-0410-ace0-fbb531ad65f3