Eliminates doubling the :port part of SIP Notify Message-Account headers.

This patch prevents the domain string from getting mangled during the initreqprep
step by moving the initialization to before its immediate use.  It also documents
this pitfall for the ast_sockaddr_stringify functions.

(issue ASTERISK-19057)
Reported by: Yuri
Review: https://reviewboard.asterisk.org/r/1678/
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Merged revisions 351559 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 351560 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@351561 65c4cc65-6c06-0410-ace0-fbb531ad65f3