Commit 904b3bfe tried to fix the deletion of custom ndparams from
group, but instead broke both modification and deletion: because we
run ForceDictType on self.op.ndparams instead of the updated
new_ndparams, we can neither delete nor set properly spindle_count
(since it won't be coerced to int).

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>