Gracefully handle sftp errors

[bwachter]

Newer versions of scp internally default to using sftp, which fails if the server does not properly support sftp.

For unix like machines we usually should deploy sshd with sftp correctly configured - but Windows seems to have problems, even though it claims to support sftp.

As a workaround playbooks to hosts failing with scp upload errors can be made to work by adding --scp-extra-args="-O" to the command line, but ideally we should find a fix where things just work.