Improve consistency of party ID privacy usage.

Improve consistency of party ID privacy usage.

Prior to this change, the Remote-Party-ID header took the position of
"If caller name and number are not explicitly allowed, then they are private"
and P-Asserted-Identity took the position of
"Caller name and number are only private if marked explicitly so"

Now both mechanisms of conveying party identification use the former approach.

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/12@421778 65c4cc65-6c06-0410-ace0-fbb531ad65f3