Rehashing in ovs-workqueue can cause ovs-mutex lock contentions
in case of heavy flow setups where both needs ovs-mutex.  So by
moving rehashing to flow-setup we can eliminate contention.
This also simplify ovs locking and reduces dependence on
workqueue.
Signed-off-by: NPravin B Shelar <pshelar@nicira.com>
Signed-off-by: NJesse Gross <jesse@nicira.com>