This restores OVS_DEFAULT to the BASE_RESOURCE_MAP.
There were some changes in commit ad7f870c that moved OVS_DEFAULT
out of the BASE_RESOURCE_MAP, which resulted in no more rendering
of /etc/default/openvswitch-switch for non-DPDK deployments.
Closes-Bug: #1925962
Change-Id: I8bc6e0c20e5702db5a44fda531b6a59ada5bee1e