Fix file descriptor leak in RTP code.

SIP requests that offered codecs incompatible with configured values
could result in the allocation of RTP and RTCP ports that would not get
reclaimed later.

ASTERISK-24666 #close
Reported by Y Ateya

Review: https://reviewboard.asterisk.org/r/4323

AST-2015-001
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Merged revisions 431300 from http://svn.asterisk.org/svn/asterisk/branches/12
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Merged revisions 431303 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@431304 65c4cc65-6c06-0410-ace0-fbb531ad65f3