Sometimes vsftpd returns a 426 error when closing the stream even when
all the data has been transferred successfully. This is some TLS
protocol mismatch.
Rclone has code to deal with this already, but the error returned from
Close was wrapped in a multierror so the detection didn't work.
This properly extract `textproto.Error` from the errors returned by
`github.com/jlaffaye/ftp` in all the cases.
See: https://forum.rclone.org/t/vsftpd-vs-rclone-part-2/36774
If mkdir fails then before this change it would have thrown an
error.
After this change, if the error indicated that the directory
already exists then the error is not returned to the user.
This fixes a race condition when two rclone threads are trying to
create the same directory.
LesmiscoreandGitHub
