Improve l2_macs_events API to provide MAC move information

Change mac_entry layout in l2_macs_event API message so the MAC
entry can be either add, delete or move where the sw_if_index of
an existing MAC entry changed. Also added a 8-bit flags field
in mac_entry for any future expansion.

Change-Id: I3bf9e1cf2556f2938202025a5d0772c2ce2fc99f
Signed-off-by: John Lo <loj@cisco.com>
diff --git a/src/vnet/l2/l2_learn.c b/src/vnet/l2/l2_learn.c
index 6ece1a3..04e0721 100644
--- a/src/vnet/l2/l2_learn.c
+++ b/src/vnet/l2/l2_learn.c
@@ -207,6 +207,7 @@
 	  result0->fields.age_not = 0;
 	}
       result0->fields.lrn_evt = (msm->client_pid != 0);
+      result0->fields.lrn_mov = (msm->client_pid != 0);
       counter_base[L2LEARN_ERROR_MAC_MOVE] += 1;
     }