ofagent: Enable local arp responder for local VMs

Because ofagent makes every arp requests packet-in and
perform packet-out anyway, just make it respond arp requests
for local VMs.  It would be simpler and more effective than
forwarding requests to the network as it did before this change.

As a bonus, now we can test l2pop and local arp responder with
a single node setup, at least for some extents.

Related: blueprint ofagent-l2pop
Related: blueprint ofagent-merge-bridges
Change-Id: I606a238d8c2021ed908fbd89d3488768497f57c5
l2pop: Allow network types overridable

Currenly "tunnel_types" is used for two different purposes; l2pop and
check_segment_for_agent.  This commit introduces a new agent
configuration "l2pop_network_types" to allow overriding the former.

This will be used by ofagent, which wants l2pop info for TYPE_VLAN
as well.

Related: blueprint ofagent-l2pop
Related: blueprint ofagent-merge-bridges
Change-Id: Ia83a94b6661aa36afa8bfeb073101171ffde62a9
ofagent: Local arp responder for VLAN

Implement local arp responder for non-tunnel network types.
Enable it for VLAN by requesting l2pop for VLAN.

Related: blueprint ofagent-l2pop
Related: blueprint ofagent-merge-bridges
Change-Id: I2f200a1ae2bd769ea1f83fe65e58e82325ed92b0
Remove unneeded device_owner field from l2pop tuple

The DVR development added this device_owner to the middle of this
tuple during early development because it was thought to be needed.
Over the course of development, it was found to be unnecessary and
much of the code that read it from this value was removed or
obsoleted.  That job went unfinished and so this commit completes it.
This essentially restores the code to what it was before and fixes the
regression that was caused.

Change-Id: Ia901f925883b53e9880dd25688e16e0ffe402bf4
Partial-bug: #1352801