res_pjsip_exten_state: Reduce log clutter... change a WARNING to a VERBOSE/2

Reduce log clutter by changing the "Watcher for hint %s (removed|deactivated)"
message from WARNING to VERBOSE/2.

Tested-by: George Joseph

Review: https://reviewboard.asterisk.org/r/4387/
........

Merged revisions 431403 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@431404 65c4cc65-6c06-0410-ace0-fbb531ad65f3