Log babysitter pid and shutdown request.

Note that cluster_run starts babysitters via
child_erlang:start_child/1 which also prints this information, so in
such case it will be duplicated.

Change-Id: I6078b19ffc6459336fca0303e0d6cd344ec37885
Reviewed-on: http://review.couchbase.org/43495
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>