Move handling of 408 response so there is no misleading warning message.

(closes issue ASTERISK-20060)
Reported by: Walter Doekes
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Merged revisions 373848 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 373849 from http://svn.asterisk.org/svn/asterisk/branches/10
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Merged revisions 373850 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@373852 65c4cc65-6c06-0410-ace0-fbb531ad65f3