Interim working version with backfill reserve state changes

Signed-off-by: David Zafman <david.zafman@inktank.com>
Return false for func that returns bool

Signed-off-by: David Zafman <david.zafman@inktank.com>
Change waiting_on_backfill to a set<int>

Signed-off-by: David Zafman <david.zafman@inktank.com>