chan_sip: Increase some scratch buffer sizes dealing with caller id.

* Eliminated an unnecessary initialization in check_user_full().

(closes issue ASTERISK-22477)
Reported by: Michael Shepelev


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/1.8@400013 f38db490-d61c-443f-a65b-d21fe96a405b