handlers: add some logging
handlers: add some logging

Small addition to the parent commit.  I figured we might also benefit
from a log line in RequestHandler.stop, since it took a while to realise
that might hang (see #218).

Signed-off-by: Yung-Chin Oei <e4c1ab9da74060df152545062ee274845648ed6c@yungchin.nl>

thedrow/samsa,wikimedia/operations-debs-python-pykafka,wikimedia/operations-debs-python-pykafka,yungchin/pykafka,yungchin/pykafka,benauthor/pykafka,thedrow/samsa,benauthor/pykafka,thedrow/samsa,benauthor/pykafka,wikimedia/operations-debs-python-pykafka