cmd/docker: only parse global arguments once.

Before calling `cmd.Execute` we need to reset the arguments to be used to not
include the global arguments which we have already parsed. This is precisely
the `args` which we have in our hand at this point.

This fixes `TestGlobalArgsOnlyParsedOnce/builtin` in the cli-plugins e2e tests.

`TestGlobalArgsOnlyParsedOnce/plugin` is still broken will be fixed next.

Signed-off-by: Ian Campbell <ijc@docker.com>

cmd/docker/docker.go

@@ -228,6 +228,9 @@ func runDocker(dockerCli *command.DockerCli) error {
 		}
 	}
 
+	// We've parsed global args already, so reset args to those
+	// which remain.
+	cmd.SetArgs(args)
 	return cmd.Execute()
 }