Add 's' option to ChanSpy, which makes the app exit when no channels are left to spy on.

(closes issue #14594)
Reported by: JimDickenson
Patches:
      chanspy.diff uploaded by JimDickenson (license 710)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@203842 65c4cc65-6c06-0410-ace0-fbb531ad65f3