chan_sip: Fix dialog reference leaked to scheduler for reinvite_timeout.

chan_sip: Fix dialog reference leaked to scheduler for reinvite_timeout.

Release the scheduler reference to the dialog for reinvite timeout during
dialog_unlink_all.

ASTERISK-24876 #close
Reported by: Corey Farrell
Review: https://reviewboard.asterisk.org/r/4491/
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Merged revisions 433112 from http://svn.asterisk.org/svn/asterisk/branches/11
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Merged revisions 433113 from http://svn.asterisk.org/svn/asterisk/branches/13

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@433114 65c4cc65-6c06-0410-ace0-fbb531ad65f3