Fixes to fabric.p4 pipeline

- Fix ethernet matching fields in ACL (dst and src were inverted)
- When doing punt_to_cpu after setting a multicast group clear the mcast_grp metadata field

Change-Id: I456566929b118188a1b2a40ff3f4de4c6c63d5bb
diff --git a/pipelines/fabric/impl/src/main/resources/include/bng.p4 b/pipelines/fabric/impl/src/main/resources/include/bng.p4
index 5deb8ee..29537bf 100644
--- a/pipelines/fabric/impl/src/main/resources/include/bng.p4
+++ b/pipelines/fabric/impl/src/main/resources/include/bng.p4
@@ -42,6 +42,9 @@
 
     action punt_to_cpu() {
         smeta.egress_spec = CPU_PORT;
+        // Clean the multicast group, otherwise multicast decision
+        //  will override the punting to CPU action
+        smeta.mcast_grp = 0;
         c_control.count(fmeta.bng.line_id);
     }