ofp-actions: Support mixing "conjunction" and "note" actions.

ofp-actions: Support mixing "conjunction" and "note" actions.

It doesn't make sense to mix "conjunction" actions with most other kinds
of actions.  That's because flows with "conjunction" actions aren't ever
actually executed, so any actions mixed up with them would never do
anything useful.  "note" actions are a little different because they never
do anything useful anyway: they are just there to allow a controller to
annotate flows.  It makes as much sense to annotate a flow with
"conjunction" actions as it does to annotate any other flow, so this
commit makes this possible.

Requested-by: Soner Sevinc <sevincs@vmware.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Andy Zhou <azhou@nicira.com>