ofproto: Delete all groups and meters when (un)configuring a controller.

ofproto: Delete all groups and meters when (un)configuring a controller.

Open vSwitch has always deleted all flows from the flow table whenever a
controller is configured or whenever all the controllers are unconfigured.
After this commit, OVS additionally deletes all OpenFlow groups and meters.

Suggested-by: Periyasamy Palanisamy <periyasamy.palanisamy@ericsson.com>
Suggested-by: Jan Scheurich <jan.scheurich@ericsson.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: Jan Scheurich <jan.scheurich@ericsson.com>
Tested-by: Jan Scheurich <jan.scheurich@ericsson.com>
Reviewed-by: Greg Rose <gvrose8192@gmail.com>
Tested-by: Greg Rose <gvrose8192@gmail.com>