delete plugin rootfs on plugin rm

Signed-off-by: Victor Vieux <vieux@docker.com>

integration-cli/docker_cli_plugins_test.go

@@ -27,6 +27,7 @@ func (s *DockerSuite) TestPluginBasicOps(c *check.C) {
 	c.Assert(out, checker.Contains, "true")
 
 	id, _, err := dockerCmdWithError("plugin", "inspect", "-f", "{{.Id}}", pNameWithTag)
+	id = strings.TrimSpace(id)
 	c.Assert(err, checker.IsNil)
 
 	out, _, err = dockerCmdWithError("plugin", "remove", pNameWithTag)

plugin/backend.go

@@ -162,6 +162,7 @@ func (pm *Manager) Remove(name string, config *types.PluginRmConfig) error {
 	}
 
 	pm.pluginStore.Remove(p)
+	os.RemoveAll(filepath.Join(pm.libRoot, p.GetID()))
 	pm.pluginEventLogger(p.GetID(), name, "remove")
 	return nil
 }