Fix IPv4 ecn packet parsing.

This commit removes wrong byte shifting.
Add matching of masked vlan_id field.

This commit adds the missing case of matching flows
with a masked vlan_id field.
Fix the multiple vlan push.

This commit adds a slightly change to
the vlan tag reconstruction to reconsider the
case when there is another vlan tag after the
one being reconstructed.
Fix vlan pcp parsing.