baremetal: Drop unused columns in bm_nodes

Drop these two columns:
* bm_nodes.prov_vlan_id
* bm_nodes.registration_status

And update related code, tests and api_samples.

Change-Id: Iadefc83a00ad9ae5a3bb39f357080299875bdf09
Merge "baremetal: Drop unused columns in bm_nodes"