How best to deal with SFTP servers responding FAILURE, rather than a more specific status

(continuation of [ Paramiko server responds to stat() with FAILURE rather than NO_SUCH_FILE #817](https://github.com/hierynomus/sshj/issues/817))

Various servers respond to requests with FAILURE instead of responding with a more specific error (as suggested in the standard )

Examples are:
SSH2-paramiko responds to stat() with FAILURE instead of NO_SUCH_FILE
SSH2-OpenSSH responds to mkdir() with FAILURE instead of FILE_ALREADY_EXISTS (thanks @vladimirlagunov)

I am sure there are many other cases.

A general method for dealing with these vagaries without affecting the core of SSH4J-SFTP would be highly advantageous in dealing promptly with suchlike problems.

I propose to launch a discussion here, prior to development.