VPP-574: fix the MACIP ACLs blocking ARP traffic

VPP-574: fix the MACIP ACLs blocking ARP traffic

The initial assumption was that the MACIP ACL classifier tables would be applied
after the classification of the traffic based on the ethertype, it turned out
to be untrue, but the fix in the code did not happen.

Add the ethertype to the mask, and the logic to create the ACL classifier tables
permitting the ARP ethertype with the correct payload.

Change-Id: I7c05c7893f6df8258998eed8983056c77586df81
Signed-off-by: Andrew Yourtchenko <ayourtch@gmail.com>