Ensure Shutdown AMI event is still fired during Asterisk shutdown

Richard pointed out that having the manager dispose of itself gracefully
during shutdown meant that the Shutdown event will no longer get fired.
This patch moves the AMI event just prior to running the atexit callbacks.
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Merged revisions 374230 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 374231 from http://svn.asterisk.org/svn/asterisk/branches/10
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Merged revisions 374248 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@374259 65c4cc65-6c06-0410-ace0-fbb531ad65f3