Reuse current spindles in design for partitioned

Reuse current spindles in design for partitioned

Renaming the current parameters dealing with spindles is nice, as their
meaning would be clearer, but that would mean changing a lot of code,
change external interfaces, and renaming internal variables for little
benefit. Also, instance policies would end up containing two related
parameters, one used when exclusive_storage is enabled, and the other when
disabled. Reusing the existing parameters by changing slightly their
semantics makes more sense.

Signed-off-by: Bernardo Dal Seno <bdalseno@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>