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

util-linux/umount.c

@@ -22,7 +22,7 @@
 //usage:     "\n	-l	Lazy umount (detach filesystem)"
 //usage:     "\n	-f	Force umount (i.e., unreachable NFS server)"
 //usage:	IF_FEATURE_MOUNT_LOOP(
-//usage:     "\n	-D	Don't free loop device even if it has been used"
+//usage:     "\n	-d	Free loop device even if it has been used"
 //usage:	)
 //usage:
 //usage:#define umount_example_usage
@@ -55,8 +55,8 @@ static struct mntent *getmntent_r(FILE* stream, struct mntent* result,
 #define OPTION_STRING           "fldDnra" "vt:i"
 #define OPT_FORCE               (1 << 0) // Same as MNT_FORCE
 #define OPT_LAZY                (1 << 1) // Same as MNT_DETACH
-//#define OPT_FREE_LOOP           (1 << 2) // -d is assumed always present
-#define OPT_DONT_FREE_LOOP      (1 << 3)
+#define OPT_FREELOOP            (1 << 2)
+//#define OPT_DONT_FREE_LOOP    (1 << 3) // Default behavior
 #define OPT_NO_MTAB             (1 << 4)
 #define OPT_REMOUNT             (1 << 5)
 #define OPT_ALL                 (ENABLE_FEATURE_UMOUNT_ALL ? (1 << 6) : 0)
@@ -173,7 +173,7 @@ int umount_main(int argc UNUSED_PARAM, char **argv)
 		} else {
 			// De-allocate the loop device.  This ioctl should be ignored on
 			// any non-loop block devices.
-			if (ENABLE_FEATURE_MOUNT_LOOP && !(opt & OPT_DONT_FREE_LOOP) && m)
+			if (ENABLE_FEATURE_MOUNT_LOOP && (opt & OPT_FREELOOP) && m)
 				del_loop(m->device);
 			if (ENABLE_FEATURE_MTAB_SUPPORT && !(opt & OPT_NO_MTAB) && m)
 				erase_mtab(m->dir);