fs-mistrust: Handle windows prefixes specially.
On Windows, paths can have a "prefix", like C:
or
\\server\share
. Attempts to get metadata for these prefixes
appear to fail with ERROR_INVALID_FUNCTION
, since they are not
files.
This patch teaches fs-mistrust about prefixes on Windows, and tells it that attempts to find their metadata are allowed to fail.
Doing this may solve part of #557 (closed).