comet implementations inconsistent configuration/behavior

  <!-- comment out for EE comet (async) -->
	<device-config>
		<device-type>ajax</device-type>
		<server-push-class>org.zkoss.zkex.ui.comet.CometServerPush</server-push-class>
	</device-config>

	<preference>
		<name>CometServerPush.retry.delay</name>
		<value>3000</value><!-- 3 seconds delay between each retry-->
	</preference>
	<preference>
		<name>CometServerPush.retry.count</name>
		<value>3</value><!-- 3 tries for each request -->
	</preference>
	<preference>
		<name>CometServerPush.ajax.timeout</name>
		<value>5000</value><!-- 5 sec -->
	</preference>