Need a test for vhost user interface management using HC + VPP.

Test scenario:
1. Read all interfaces

• According to "List ifcs - oper" request from HC postman collection
• should succeed and list initial VPP interface(s)
  2. Create vhost user ifc
• According to "Add vhost user ifc - cfg" request from HC postman collection
• should succeed
  3. Read all interfaces
• as step 1
• should list the vhost user interface with same configuration as was in step 2
  4. Read specifically the vhost user interface
• http://localhost:8181/restconf/operational/ietf-interfaces:interfaces-state/interface/vhost1
• should provide subset of data from step 3, just the vhostuser
  4. Modify the vhost user interface
• According to "Modify vhost user ifc - cfg" request from HC postman collection
  5. Repeat step 3
• check updated config
  6. Delete the interface
• According to "Delete vhost user ifc - cfg" request from HC postman collection
• should succeed
  7. Read all interfaces
• as in step 1
• the vhost user ifc should disappear

POSTMAN collection: https://git.fd.io/cgit/honeycomb/plain/v3po/postman_rest_collection.json