[Virtio-fs] write permissions for Windows host on Linux guest

[birnenkram at posteo.de]

One more thought after some further digging: This issue is very likely 
related to how WinFsp maps the permissions between Windows and Linux (so 
indeed whether one runs the shell as Administrator or not on the Windows 
guest would matter). See 
http://www.secfs.net/winfsp/doc/SSHFS-Port-Case-Study. The question is 
now how to "make it work" and whether this requires an update of WinFsp 
itself.