Use TrimSpace to instead of Trim

String.Trim(string, " ") can only get ride of the blank, but actully we need
to remove all leading and trailing white space include "\t" for example.

Prior to this patch, one can login with "[Tab][Tab]username", and it will
not be consider as the same with "username".

Signed-off-by: Hu Keping <hukeping@huawei.com>
Upstream-commit: e9602f3561b78313c4d474a8d950f7cc562637e8
Component: engine

components/engine/api/client/login.go

@@ -64,7 +64,7 @@ func (cli *DockerCli) CmdLogin(args ...string) error {
 	if username == "" {
 		promptDefault("Username", authconfig.Username)
 		username = readInput(cli.in, cli.out)
-		username = strings.Trim(username, " ")
+		username = strings.TrimSpace(username)
 		if username == "" {
 			username = authconfig.Username
 		}