revalidator: Distinguish new and duplicate flows.

We previously counted flows that have been installed during the current
dump as duplicates, rather than recognising them as new flows. This
patch separates the counters out for these two cases.

Signed-off-by: Joe Stringer <joestringer@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>
tests: Mention binomial coefficient in hash tests.

This just makes it a bit easier for someone coming in fresh to do some
searches and figure out what the description means.

Signed-off-by: Joe Stringer <joestringer@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>