fix: make sure to correctly initialize health checks (#17765)

health checks were missing for drives replaced since

- HealFormat() would replace the drives without a health check
- disconnected drives when they reconnect via connectEndpoint()
  the loop also loses health checks for local disks and merges
  these into a single code.
- other than this separate cleanUp, health check variables to avoid
  overloading them with similar requirements.
- also ensure that we compete via context selector for disk monitoring
  such that the canceled disks don't linger around longer waiting for
  the ticker to trigger.
- allow disabling active monitoring.

cmd/bucket-targets.go

@@ -58,7 +58,7 @@ type epHealth struct {
 }
 
 // isOffline returns current liveness result of remote target. Add endpoint to
-// healthcheck map if missing and default to online status
+// healthCheck map if missing and default to online status
 func (sys *BucketTargetSys) isOffline(ep *url.URL) bool {
 	sys.hMutex.RLock()
 	defer sys.hMutex.RUnlock()
@@ -126,7 +126,7 @@ func (sys *BucketTargetSys) heartBeat(ctx context.Context) {
 	}
 }
 
-// periodically rebuild the healthcheck map from list of targets to clear
+// periodically rebuild the healthCheck map from list of targets to clear
 // out stale endpoints
 func (sys *BucketTargetSys) reloadHealthCheckers(ctx context.Context) {
 	m := make(map[string]epHealth)
@@ -362,7 +362,7 @@ func NewBucketTargetSys(ctx context.Context) *BucketTargetSys {
 		hc:            make(map[string]epHealth),
 		hcClient:      newHCClient(),
 	}
-	// reload healthcheck endpoints map periodically to remove stale endpoints from the map.
+	// reload healthCheck endpoints map periodically to remove stale endpoints from the map.
 	go func() {
 		rTimer := time.NewTimer(defaultHealthCheckReloadDuration)
 		defer rTimer.Stop()