osd(9): Change array pointer to array pointer type from void*

This is a minor follow-up to r297422, prompted by a Coverity warning. (It's
not a real defect, just a code smell.) OSD slot array reservations are an
array of pointers (void **) but were cast to void* and back unnecessarily.
Keep the correct type from reservation to use.

osd.9 is updated to match, along with a few trivial igor fixes.

Reported by: Coverity
CID: 1353811
Sponsored by: EMC / Isilon Storage Division