- Simplify the volume-deletion code in RawCheckForDismount().
- Fixes the OpenCount check in RawClose(): the VCB mutex must be
released when the volume has not been dismounted, either because
OpenCount != 0 or because RawCheckForDismount() returned FALSE.
- Explicitly use VCB_STATE_LOCKED instead of hardcoding its value.
- In IRP_MN_VERIFY_VOLUME handling, lock the volume before playing
with it, and again let the volume be dismounted only if OpenCount == 0
(and the IoDeleteDevice() call is done by RawCheckForDismount()).