do not block iam.store registration (#18999)

current implementation would quite simply
block the sys.store registration, making
sys.Initialized() call to be blocked.

cmd/erasure-healing_test.go

@@ -1645,7 +1645,6 @@ func TestHealLastDataShard(t *testing.T) {
 
 			_, err = obj.PutObject(ctx, bucket, object,
 				mustGetPutObjReader(t, bytes.NewReader(data), int64(len(data)), "", ""), opts)
-
 			if err != nil {
 				t.Fatal(err)
 			}