Fix CPU spike when pressing DTMF after agent login.

Fix CPU spike when pressing DTMF after agent login.

The problem here is that DTMF was being continuously deferred and requeued
since ast_safe_sleep is called in a loop. There are serveral other places in the
code that sleeps and then loops in a similar fashion. Because of this fact I
opted to not defer DTMF any more, which will not affect the original fix:

https://reviewboard.asterisk.org/r/674

(closes issue #18130)
Reported by: rgj

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@301502 65c4cc65-6c06-0410-ace0-fbb531ad65f3