improve: eager informer start check

this is important for dynamic event source registration to not reindex resources

Signed-off-by: Attila Mészáros <a_meszaros@apple.com>

Author: csviri

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/InformerEventSource.java

@@ -139,6 +139,9 @@ protected void handleEvent(
 
   @Override
   public synchronized void start() {
+    if (isRunning()) {
+      return;
+    }
     super.start();
     // this makes sure that on first reconciliation all resources are
     // present on the index