Add log message for unexpected errors
Add log message for unexpected errors

This patch modifies Kuryr to emit the error log message when it
experiences errors that are not handled in the request handlers.

Change-Id: I9f4c997cb1ae74567803d4ce5b8a7cdc9f1c2653
Signed-off-by: Taku Fukushima <d385cb54d860d8a5dcc6157b54cf213091772451@gmail.com>

celebdor/kuryr,openstack/kuryr,openstack/kuryr,celebdor/kuryr-libnetwork,midonet/kuryr,midonet/kuryr,celebdor/kuryr-libnetwork,celebdor/kuryr-libnetwork,celebdor/kuryr,midonet/kuryr