mod_sofia: Add url encode to a var in the xml output to be valid xml.  Also changed switch_url_encode to return the pointer of the string rather than the length, same as switch_amp_encode()


git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@17087 d0543943-73ff-0310-b7d9-9358b9ac24b2