EthernetFace: avoid putting the NIC in promiscuous mode if possible.

Try to use the PACKET_ADD_MEMBERSHIP socket option and the
SIOCADDMULTI ioctl, and only if they fail or are not available
we fall back to promiscuous mode.

Change-Id: Ib534e161ff86ca855e084240b94a166bc4d33ce1
Refs: #1278