ofproto: Finalize all ofoperations in a given ofgroup at the same time.

ofproto: Finalize all ofoperations in a given ofgroup at the same time.

An upcoming commit will add support for flow table monitoring by
controllers.  One feature of this upcoming support is that a controller's
own changes to the flow table can be abbreviated to a summary, since the
controller presumably knows what it has already sent to the switch.
However, the summary only makes sense if a set of flow table changes
completely succeeds or completely fails.  If it partially fails, the
switch must not attempt to summarize it, because the controller needs
to know the details.  Given that, we have to wait for all of the
operations in an ofgroup to either succeed or fail before the switch
can send its flow table update report to the controllers.  This
commit makes that change.

Signed-off-by: Ben Pfaff <blp@nicira.com>