net=host: remove /var/run/docker/netns/default from OCI config

Prior to this commit, a container running with `--net=host` had
`{"type":"network","path":"/var/run/docker/netns/default"}` in
the ``.linux.namespaces` field of the OCI Runtime Config,
but this wasn't needed.

Close issue 47100

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

daemon/oci_linux.go

@@ -285,10 +285,7 @@ func WithNamespaces(daemon *Daemon, c *container.Container) coci.SpecOpts {
 					})
 				}
 			case networkMode.IsHost():
-				setNamespace(s, specs.LinuxNamespace{
-					Type: specs.NetworkNamespace,
-					Path: c.NetworkSettings.SandboxKey,
-				})
+				oci.RemoveNamespace(s, specs.NetworkNamespace)
 			default:
 				setNamespace(s, specs.LinuxNamespace{
 					Type: specs.NetworkNamespace,