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>
Use ~s for os:getpid().

os:getpid() returns a string. So using ~p leaves double quotes around
the value.

Change-Id: Ie2a509aa2709e611cd801e37b4987886662112ef
Reviewed-on: http://review.couchbase.org/43496
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>