Add a column to the repair queue table in the satellite db for healthy
piece count. When an item is selected from the repair queue, the least
durable segment that has not been attempted in the past hour should be
selected first. This prevents our repairer from getting stuck doing work
on segments that are close to the repair threshold while allowing
segments that are more unhealthy to degrade further.
The migration also clears the repair queue so that the migration runs
quickly and we can properly account for segment health in future repair
work.
We do not select items off the repair queue that have been attempted in
the past six hours. This was changed from on hour to allow us time to
try a wider variety of segments when the repair queue is very large.
Change-Id: Iaf183f1e5fd45cd792a52e3563a3e43a2b9f410b
