pjsip outbound registration: Log message says received a 408 when we didn't

pjsip outbound registration: Log message says received a 408 when we didn't

If the server didn't exist that we are trying to register to the log message
would say that a 408 was received from that server when in reality one wasn't.
Added log messages stating no response was received if the response does not
exist.

(closes issue ASTERISK-22554)
Reported by: Rusty Newton
Review: https://reviewboard.asterisk.org/r/2893/

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/12@400890 65c4cc65-6c06-0410-ace0-fbb531ad65f3