allow background IAM load to speed up startup (#9796)

Also fix healthcheck handler to run success
only if object layer has initialized fully
for S3 API access call.

cmd/iam-object-store.go

@@ -588,14 +588,6 @@ func listIAMConfigItems(ctx context.Context, objAPI ObjectLayer, pathPrefix stri
 				return
 			}
 
-			// Attempt a slow down load only when server is
-			// active and initialized.
-			if !globalSafeMode {
-				// Slow down listing and loading for config items to
-				// reduce load on the server
-				waitForLowHTTPReq(int32(globalEndpoints.NEndpoints()))
-			}
-
 			marker = lo.NextMarker
 			lister := dirList(lo)
 			if !dirs {