Having a more detailed log of the interaction between client and
server is invaluable in debugging how meta context negotiation
actually works.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180330130950.1931229-1-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>