ofproto-dpif: Update 'facet->rule' stats in facet_push_stats().

ofproto-dpif: Update 'facet->rule' stats in facet_push_stats().

Before this patch, stats for 'facet->rule' were handled differently
than stats which 'facet' resubmitted into.  The former were
maintained in 'facet' until it was destroyed, while the latter were
pushed regularly in facet_push_stats().

This inconsistent behavior was not only confusing, it was often
incorrect.  In some circumstances, if a facet changed rules, it
could carry the statistics from the entirety of its lifetime from
the old rule to the new one.  This patch remedies the issue by
handling all rule stats in facet_push_stats().

Reported-by: Tmusic <Tmusic987@gmail.com>
Signed-off-by: Ethan Jackson <ethan@nicira.com>