Remove duplicated "caught" message

The affected messge is duplicated in _wait_for_exit_or_signal.  Since
INFO doesn't log it's source function it can be confusing as to where
this log output actually came from.

See also https://review.openstack.org/#/c/85639/

Change-Id: Ic4ff6321559cd484b722955c70d0db776e3e6620
Merge "Remove duplicated "caught" message"