fix t5600-clone-fail-cleanup.sh on windows
fix t5600-clone-fail-cleanup.sh on windows

In windows you cannot remove current or opened directory,
an opened file, a running program, a loaded library, etc...

[jc: signoffs?  With a minor quoting fix.]

Signed-off-by: Junio C Hamano <dc50d1021234060e53ec42a77d526afa2fe07479@cox.net>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git