acl-plugin: VPP-1088: add support for egress filter in macip ACLs

This is the second patch, using the new functionality from the change 10002
in order to implement the egress filtering on the MACIP ACLs.

This adds an action "2" which means "add also egress filtering rules for this
MACIP ACL.

The reason for having the two choices is that the egress filtering really takes
care of a fairly corner case scenario, and I am not convinced that
always adding the performance cost of the egress lookup check is worth it.

Also, of course, not breaking the existing implementations is a nice plus,
too.

Change-Id: I3d7883ed45b1cdf98d7303771bcc75951dff38f0
Signed-off-by: Andrew Yourtchenko <ayourtch@gmail.com>