Fix handling of unsupported namespaces

currentState() always adds all possible namespaces to the state,
regardless of whether they are supported.
If orderNamespacePaths detects an unsupported namespace, an error is
returned that results in initialization failure.

Fix this by only adding paths of supported namespaces to the state.

Signed-off-by: Ido Yariv <ido@wizery.com>

libcontainer/container_linux.go

@@ -1064,6 +1064,9 @@ func (c *linuxContainer) currentState() (*State, error) {
 			state.NamespacePaths[ns.Type] = ns.GetPath(pid)
 		}
 		for _, nsType := range configs.NamespaceTypes() {
+			if !configs.IsNamespaceSupported(nsType) {
+				continue
+			}
 			if _, ok := state.NamespacePaths[nsType]; !ok {
 				ns := configs.Namespace{Type: nsType}
 				state.NamespacePaths[ns.Type] = ns.GetPath(pid)