Fix api trace replay of handler to pass vm parameter

Fix api trace replay of handler to pass vm parameter

I suppose most API handlers do not use vm parameter so it has not
been a problem so far. Now vl_api_vnet_set_ip6_ethernet_neighbor()
was crashing when called from api trace replay because either of
ip_neighbor_add_del_t_handler() vnet_arp_set_ip4_over_ethernet()
need vm to be correct when it calls vlin_time_now() to update the
neighbor timestamp.

Change-Id: Iffb2084a7c90f92c4b86b339ea11800dd41117eb
Signed-off-by: John Lo <loj@cisco.com>