ofproto-dpif: Use ovs_refcount_try_ref_rcu().

ofproto-dpif: Use ovs_refcount_try_ref_rcu().

This is a prerequisite step in making the classifier lookups lockless.
If taking a reference fails, we do the lookup again, as a new (lower
priority) rule may now match instead.

Also remove unwildcarding dl_type and nw_frag, as these are already
taken care of by xlate_actions().

Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>