ftp: check connection before returning it to the pool #1435
ftp: check connection before returning it to the pool #1435

If the last FTP command caused an error, and if the error wasn't a
regular FTP error code, then we check the connection is working using
a NOOP call before returning it to the connection pool.

olihey/rclone,seuffert/rclone,B4dM4n/rclone,yonjah/rclone,yonjah/rclone,olihey/rclone,seuffert/rclone,ncw/rclone,ncw/rclone,B4dM4n/rclone,yonjah/rclone,yonjah/rclone,ncw/rclone,olihey/rclone,B4dM4n/rclone,B4dM4n/rclone,olihey/rclone,seuffert/rclone,ncw/rclone,seuffert/rclone