res_pjsip_pidf_body_generator / res_pjsip_xpidf_body_generator: Ensure local entity is unquoted.

The local entity as provided by PJSIP is quoted within '<' and '>'. As a result placing
this value into XML will result in malformed XML being produced. This patch now unquotes
the local entity so it can go safely into the XML.

Review: https://reviewboard.asterisk.org/r/3851/
........

Merged revisions 419750 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@419751 65c4cc65-6c06-0410-ace0-fbb531ad65f3