More improvements to re-INVITEs timing out after a provisional response

More improvements to re-INVITEs timing out after a provisional response

There is no need to call check_pendings() on a final response to an INVITE
when destroying the scheduler entry as it will be done later during normal
processing.

(issue ASTERISK-19992)
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Merged revisions 369579 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 369580 from http://svn.asterisk.org/svn/asterisk/branches/10

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@369581 65c4cc65-6c06-0410-ace0-fbb531ad65f3