Handle read/quorum errors when initializing all subsystems (#6585)

- Only require len(disks)/2 to initialize the cluster
- Fix checking of read/write quorm in subsystems init
- Add retry mechanism in policy and notification to avoid aborting in case of read/write quorums errors

cmd/xl-sets.go

@@ -174,7 +174,7 @@ func (s *xlSets) reInitDisks(refFormat *formatXLV3, storageDisks []StorageAPI, f
 // any given sets.
 func (s *xlSets) connectDisksWithQuorum() {
 	var onlineDisks int
-	for onlineDisks < (len(s.endpoints)/2)+1 {
+	for onlineDisks < len(s.endpoints)/2 {
 		for _, endpoint := range s.endpoints {
 			if s.isConnected(endpoint) {
 				continue