Issue eclipse-ee4j#2016 Prevent HTTP/2 push when globally disabled

Streams still allowed pushing resources when globally disabled as the
stream itself and the session both allow it. This change makes the
stream also respect the global configuration.

Signed-off-by: Matthew Gill <matthew.gill@live.co.uk>
Signed-off-by: David Matejcek <dmatej@seznam.cz>

modules/http2/src/main/java/org/glassfish/grizzly/http2/Http2Session.java

@@ -1,5 +1,6 @@
 /*
- * Copyright (c) 2012, 2020 Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, 2020 Oracle and/or its affiliates and others.
+ * All rights reserved.
  *
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Public License v. 2.0, which is available at
@@ -489,7 +490,7 @@ void setPeerMaxConcurrentStreams(int peerMaxConcurrentStreams) {
      * Push is enabled by default.
      */
     public boolean isPushEnabled() {
-        return pushEnabled;
+        return pushEnabled && http2Configuration.isPushEnabled();
     }
 
     /**