datapath: update exact match lookup hash value to avoid hash collision

datapath: update exact match lookup hash value to avoid hash collision

Currently, the exact match cache lookup uses 'skb->hash' as an index.
In most cases, this value will be the same for pre and post
recirculation lookup, threshing the exact match cache. This patch
avoid this hash collision by using the rehashed value, by mixing in
in the 'recirc_id', as the lookup index.

Signed-off-by: Andy Zhou <azhou@nicira.com>
Acked-by: Pravin B Shelar <pshelar@nicira.com>