[FASTFAT]

[FASTFAT]
- Implement VPB swapout in our FAT driver for dismout (see VfatCheckForDismount)
- Dereference volume handles on close (not on cleanup)
- Keep track of the VDO in our VCB
- Let VfatCheckForDismount() do the actual dismount, instead of VfatDismountVolume() which just initiates it

CORE-8732 #comment Can you retry?

svn path=/trunk/; revision=65372