Instead of iterate through all dialogs, add two separte container for needdestroy...

Instead of iterate through all dialogs, add two separte container for needdestroy and rtptimeout

adding two dialog container, one for dialogs which need destroy, another for rtptimeout checks.
both container will be checked on every loop of do_monitor instead of iterate through all dialogs.

(closes issue #17912)
Reported by: schmidts
Tested by: schmidts

Review: https://reviewboard.asterisk.org/r/917/

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@288063 65c4cc65-6c06-0410-ace0-fbb531ad65f3