Fixing Arista CLI command

A minor change is made to the Arista API between ML2 Driver and the
back-end. This fix addresses this change to align Icehouse release with
Arista EOS releases.

Change-Id: Ia7cd3701c76d920a7e0d1334290c73ce7e8e5576
Closes-Bug: 1301093
(cherry picked from commit f3e9b6d6dc53d2e85c9085a1e3ec11b51f803948)
Stop using portbindings_db in BSN ML2 driver

Avoids using the portbindings_db in the Big Switch
ML2 driver since ML2 has deprecated that database for
its own version that tracks the same information.

Also eliminates unnecessary 'binding_host' field since
it is now always the same as as the 'portbinding:host_id'
field.

Closes-Bug: #1300628
Change-Id: I17d47cb446cdd2e989c3e0d01b797a81309faaa7
(cherry picked from commit c70c2719d700902854ef0381cb725722ac2da05e)
Merge "Stop using portbindings_db in BSN ML2 driver" into milestone-proposed
Merge "Fixing Arista CLI command" into milestone-proposed