[DISK] Properly implement querying partition information for partition 0.

[DISK] Properly implement querying partition information for partition 0.
In spite of what was implemented in our NT DDK sample, this is a legit operation.

This may have been turned legit starting NT5 (reminder, our implementation is
NT4 based...). So, in this situation, just return the information about the whole
disk (and not a random size) and also, mark everything with default values.

See disk_new for an example of how it works in NT5+.

CORE-14124