Set creation timestamp using Instant

Author: brandonvin

src/test/java/cd/go/contrib/elasticagent/executors/ServerPingRequestExecutorTest.java

@@ -68,7 +68,7 @@ public void setUp() {
         when(podResource.get()).thenReturn(mockedPod);
 
         objectMetadata = new ObjectMeta();
-        objectMetadata.setCreationTimestamp(getSimpleDateFormat().format(Instant.now()));
+        objectMetadata.setCreationTimestamp(Instant.now().toString());
 
         when(mockedPod.getMetadata()).thenReturn(objectMetadata);