vswitch.ovsschema: Set bfd_status to ephemeral.
When restart openvswitch, the bfd status will be kept
before ovs-vswitchd running.  And if the ovs-vswitchd
has high workload, which will defer updating bfd status,
which not we excepted.
{"name": "Open_vSwitch",
- "version": "8.3.0",
- "cksum": "3781850481 26690",
+ "version": "8.3.1",
+ "cksum": "3012963480 26720",
"tables": {
"Open_vSwitch": {
"columns": {
"min": 0, "max": "unlimited"}},
"bfd_status": {
"type": {"key": "string", "value": "string",
- "min": 0, "max": "unlimited"}},
+ "min": 0, "max": "unlimited"},
+ "ephemeral": true},
"cfm_mpid": {
"type": {
"key": {"type": "integer"},
