Turn off plugin upgrade test when userns on

Until volume plugins can be made aware of the remapped root,
interactions with volumes created by plugin will not work as the file
ownership denies permissions to the userns remapped range.

Docker-DCO-1.1-Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com>

integration-cli/docker_cli_plugins_test.go

@@ -462,7 +462,7 @@ enabled: false`, id, name)
 }
 
 func (s *DockerSuite) TestPluginUpgrade(c *check.C) {
-	testRequires(c, DaemonIsLinux, Network, SameHostDaemon, IsAmd64)
+	testRequires(c, DaemonIsLinux, Network, SameHostDaemon, IsAmd64, NotUserNamespace)
 	plugin := "cpuguy83/docker-volume-driver-plugin-local:latest"
 	pluginV2 := "cpuguy83/docker-volume-driver-plugin-local:v2"