ofproto-dpif: Install internal rule should not change the match content.

Without this patch, the match passed into to
ofproto_dpif_add_internal_flow() are modified. The mask of dl_type will
always be converted from wildcarded match into exact match due to
calling rule_dpif_lookup_in_table(). The fix makes sure
ofproto_dpif_add_internal_flow() does not change the original match,
and makes the match passed as const in the
ofproto_dpif_add_internal_flow() API.

This bug prevents bond module from properly tracking the post
recirculation rules installed in the internal table. The existing rule
is always deleted followed by reinstalling of the same rule.

The observable behavior of the bug is that bond module losses track
of the slave's stats, after the slave is rebalanced. Although traffic
flows through the slave just fine.

Bug #1229225

Signed-off-by: Andy Zhou <azhou@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>