runtime: Check config for supported CLH (cold|hot)_plug_vfio values

The only supported options are hot_plug_vfio=root-port or no-port.
cold_plug_vfio not supported yet.

Signed-off-by: Jeremi Piotrowski <jpiotrowski@microsoft.com>

src/runtime/virtcontainers/clh_test.go

@@ -68,6 +68,7 @@ func newClhConfig() (HypervisorConfig, error) {
 		NetRateLimiterBwOneTimeBurst:  int64(0),
 		NetRateLimiterOpsMaxRate:      int64(0),
 		NetRateLimiterOpsOneTimeBurst: int64(0),
+		HotPlugVFIO:                   config.NoPort,
 	}, nil
 }