orangefs: do not wait for timeout if umounting

When the computer is turned off, all the processes are killed and then
all the filesystems are umounted.  OrangeFS should not wait for the
userspace daemon to come back in that case.

This only works for plain umount(2).  To actually take advantage of this
interactively, `umount -f' is needed; otherwise umount will issue a
statfs first, which will wait for the userspace daemon to come back.

Signed-off-by: Martin Brandenburg <martin@omnibond.com>
Signed-off-by: Mike Marshall <hubcap@omnibond.com>