ftp: add --ftp-disable-msld option to ignore MLSD for really old servers

This is useful for servers which advertise MLSD (eg some versions of
Serv-U) but don't support it properly.

See: https://forum.rclone.org/t/double-folder-names-on-target-destination-paths-ftp/18822
See: https://github.com/jlaffaye/ftp/pull/196

backend/ftp/ftp.go

@@ -85,6 +85,11 @@ to an encrypted one. Cannot be used in combination with implicit FTP.`,
 			Help:     "Disable using EPSV even if server advertises support",
 			Default:  false,
 			Advanced: true,
+		}, {
+			Name:     "disable_mlsd",
+			Help:     "Disable using MLSD even if server advertises support",
+			Default:  false,
+			Advanced: true,
 		}, {
 			Name:     config.ConfigEncoding,
 			Help:     config.ConfigEncodingHelp,
@@ -111,6 +116,7 @@ type Options struct {
 	Concurrency       int                  `config:"concurrency"`
 	SkipVerifyTLSCert bool                 `config:"no_check_certificate"`
 	DisableEPSV       bool                 `config:"disable_epsv"`
+	DisableMLSD       bool                 `config:"disable_mlsd"`
 	Enc               encoder.MultiEncoder `config:"encoding"`
 }
 
@@ -226,6 +232,9 @@ func (f *Fs) ftpConnection() (*ftp.ServerConn, error) {
 	if f.opt.DisableEPSV {
 		ftpConfig = append(ftpConfig, ftp.DialWithDisabledEPSV(true))
 	}
+	if f.opt.DisableMLSD {
+		ftpConfig = append(ftpConfig, ftp.DialWithDisabledMLSD(true))
+	}
 	if fs.Config.Dump&(fs.DumpHeaders|fs.DumpBodies|fs.DumpRequests|fs.DumpResponses) != 0 {
 		ftpConfig = append(ftpConfig, ftp.DialWithDebugOutput(&debugLog{auth: fs.Config.Dump&fs.DumpAuth != 0}))
 	}