fix: various optimizations, idiomatic changes (#9179)

- acquire since leader lock for all background operations
  - healing, crawling and applying lifecycle policies.

- simplify lifecyle to avoid network calls, which was a
  bug in implementation - we should hold a leader and
  do everything from there, we have access to entire
  name space.

- make listing, walking not interfere by slowing itself
  down like the crawler.

- effectively use global context everywhere to ensure
  proper shutdown, in cache, lifecycle, healing

- don't read `format.json` for prometheus metrics in
  StorageInfo() call.

cmd/lock-rest-server.go

@@ -293,9 +293,7 @@ func lockMaintenance(ctx context.Context, interval time.Duration) error {
 }
 
 // Start lock maintenance from all lock servers.
-func startLockMaintenance() {
-	var ctx = context.Background()
-
+func startLockMaintenance(ctx context.Context) {
 	// Wait until the object API is ready
 	// no need to start the lock maintenance
 	// if ObjectAPI is not initialized.
@@ -317,7 +315,7 @@ func startLockMaintenance() {
 	for {
 		// Verifies every minute for locks held more than 2 minutes.
 		select {
-		case <-GlobalServiceDoneCh:
+		case <-ctx.Done():
 			return
 		case <-ticker.C:
 			// Start with random sleep time, so as to avoid
@@ -357,5 +355,5 @@ func registerLockRESTHandlers(router *mux.Router, endpointZones EndpointZones) {
 		}
 	}
 
-	go startLockMaintenance()
+	go startLockMaintenance(GlobalContext)
 }