Fix parsing of SIP headers where compact and non-compact headers are mixed

Change parsing of SIP headers so that compactness of the header no longer
influences which header will be chosen.  Previously, a non-compact header
would be chosen instead of a preceeding compact-form header.

(closes issue ASTERISK-17192)
Review: https://reviewboard.asterisk.org/r/1728/
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Merged revisions 354702 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 354703 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@354704 65c4cc65-6c06-0410-ace0-fbb531ad65f3