Correct misuse of ast_strip_quoted() when getting a Diversion header's reason parameter.

The use here was assuming that the pointer would be updated, but the updated string
is actually returned by ast_strip_quoted() instead.
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Merged revisions 366597 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 366598 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@366599 65c4cc65-6c06-0410-ace0-fbb531ad65f3