Don't leak CID in From header when presentation=unavailable

When someone does Set(CALLERPRES()=unavailable) (or
Set(CALLERID(pres)=unavailable)) when sendrpid=no, the From header shows
"Anonymous" <anonymous@anonymous.invalid>. When sendrpid=yes/pai, the From
header will still display the callerid info, even though we supply an rpid
header with the anonymous info. It seems like we shouldn't leak that info in
any case. Skimming http://tools.ietf.org/html/draft-ietf-sip-privacy-04 seems
to indicate that one shouldn't send identifying info in the From in this case.

This patch anonymizes the From header as well even when sendrpid=yes/pai.

(closes issue ASTERISK-16538)

Review: https://reviewboard.asterisk.org/r/1649/
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Merged revisions 349968 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 349977 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@349978 65c4cc65-6c06-0410-ace0-fbb531ad65f3