bug in mount --move

[Roman Borisov]

Hi,

the analysis of ltp 2010 fs_bind failures showed 3 bugs.
the second test case to show mount --move issue:

the issue could be reproduced only when USE_MTAB option is switched on.

mkdir d1
busybox mount --bind d1 d1
mkdir d2
busybox mount --move d1 d2

in result we have two mount points instead of one which should be moved;

/root/tmp/d1 on /root/tmp/d1 type bind (bind)
/root/tmp/d1 on /root/tmp/d2 type bind (move)

moreover we can't umount d1 and d2 after that.

I suppose the issue is in the mount_it_now() function which must update 
/etc/mtab when mount type is "move"

Thanks,
Roman