After r254627, the deupdate() started writing the directory entries to
disk.  That has a side effect of corrupting the "." entries names on
rename, since the call to createde() in the msdosfs_rename() sets the
de_Name to the target name.  If any change to the directory attributes
is performed, the wrong name is written back to the on-disk direntry
on update.

Overwrite the de_Name for the directories on rename to correct the dot
name.

Submitted by:	bde
MFC after:	1 week
Fix a typo.

MFC after:	3 days