Skinny wasn't closing RTP sockets. This patch includes ast_rtp_instance_stop before
ast_rtp_instance_destroy which fixes the problem. Also add destroy for VRTP (which
I believe is unused, but exists).
Review: https://reviewboard.asterisk.org/r/2176/
........
Merged revisions 375660 from http://svn.asterisk.org/svn/asterisk/branches/11
git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@375663
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