openvswitch db file is created in /etc/openvswitch/conf.db. It will be
lost during upgrade openvswitch_db container.
This patch moves the db file into /var/lib/openvswitch folder, which
located in docker volume.
Change-Id: I73604fddacd21655590b9e66ee2805014795b9f1
Closes-Bug: #1649290
(cherry picked from commit f62b16f8a4)