dpif: Consistently help datapath to execute oversized actions.

Only dpif_execute() was checking for oversized actions but dpif_operate()
should do so also.  This fixes the problem.

Found by inspection.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Jesse Gross <jesse@nicira.com>
dpif: When executing an operation with help, log the sub-executes.

This should make it easier to identify problems that result from bugs in
the execution helper.

Suggested-by: Jesse Gross <jesse@nicira.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Jesse Gross <jesse@nicira.com>
dpif: Explain a bug, why it isn't important, and why it's hard to fix.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Jesse Gross <jesse@nicira.com>