Merge pull request moby#11258 from HuKeping/cmdlogin

Remove leading spaces of username when login

api/client/commands.go

@@ -344,6 +344,7 @@ func (cli *DockerCli) CmdLogin(args ...string) error {
 	if username == "" {
 		promptDefault("Username", authconfig.Username)
 		username = readInput(cli.in, cli.out)
+		username = strings.Trim(username, " ")
 		if username == "" {
 			username = authconfig.Username
 		}