umount: instead of non-standard -D, use -d with opposite meaning

This has been in upstream busybox for quite sometime, 2008-02-14 12:00:21 (GMT)
And has no negative effects on android devices.
Please see original commit:
http://git.busybox.net/busybox/commit/util-linux/umount.c?id=b2e578a1f2c3cf317b391a7d2c059d6a5f5368b8&ss=1

Change-Id: I7f8b9a6a88571b8190ffeaec75973f4ddf4f849e
1 file changed