Previously only the fs being checked on gets passed to
GetModifyWindow(). However, in most tests, the test files are
generated in the local fs and transferred to the remote fs. So the
local fs time precision has to be taken into account.
This meant that on Windows the time tests failed because the
local fs has a time precision of 100ns. Checking remote items uploaded
from local fs on Windows also requires a modify window of 100ns.
