add SslContext builder with h2 disabled

zuul-core/src/main/java/com/netflix/zuul/netty/server/http2/Http2Configuration.java

@@ -77,4 +77,28 @@ public static SslContext configureSSL(SslContextFactory sslContextFactory, Strin
 
         return sslContext;
     }
+
+    /**
+     * This is meant to be use in cases where the server wishes not to advertise h2 as part of ALPN.
+     */
+    private SslContext configureSSLWithH2Disabled(SslContextFactory sslContextFactory, String host) {
+
+        ApplicationProtocolConfig apn = new ApplicationProtocolConfig(
+                ApplicationProtocolConfig.Protocol.ALPN,
+                // NO_ADVERTISE is currently the only mode supported by both OpenSsl and JDK providers.
+                ApplicationProtocolConfig.SelectorFailureBehavior.NO_ADVERTISE,
+                // ACCEPT is currently the only mode supported by both OpenSsl and JDK providers.
+                ApplicationProtocolConfig.SelectedListenerFailureBehavior.ACCEPT,
+                ApplicationProtocolNames.HTTP_1_1);
+        final SslContext sslContext;
+        try {
+            sslContext = sslContextFactory.createBuilderForServer().applicationProtocolConfig(apn).build();
+        } catch (SSLException e) {
+            throw new RuntimeException("Error configuring SslContext with ALPN!", e);
+        }
+
+        sslContextFactory.enableSessionTickets(sslContext);
+        sslContextFactory.configureOpenSslStatsMetrics(sslContext, host);
+        return sslContext;
+    }
 }