Sometimes nodes who have gracefully exited will still be holding pieces
according to the satellite. This has some unintended side effects
currently, such as nodes getting disqualified after having successfully
exited.
* When the audit reporter attempts to update node stats, do not update
stats (alpha, beta, suspension, disqualification) if the node has
finished graceful exit (audit/reporter_test.go TestGracefullyExitedNotUpdated)
* Treat gracefully exited nodes as "not reputable" so that the repairer
and checker do not count them as healthy (overlay/statdb_test.go
TestKnownUnreliableOrOffline, repair/repair_test.go
TestRepairGracefullyExited)
Change-Id: I1920d60dd35de5b2385a9b06989397628a2f1272
de366537a8