Add ensure green to single node test

Signed-off-by: John Mazanec <[email protected]>

src/test/java/org/opensearch/knn/plugin/transport/TrainingJobRouteDecisionInfoTransportActionTests.java

@@ -51,6 +51,8 @@ public void teardown() {
 
     @SuppressWarnings("unchecked")
     public void testNodeOperation() throws IOException, InterruptedException, ExecutionException {
+        ensureGreen();
+
         // Ensure initial value of train job count is 0
         TrainingJobRouteDecisionInfoTransportAction action = node().injector()
             .getInstance(TrainingJobRouteDecisionInfoTransportAction.class);