fix(assembly): add id="broker" to sample configs so jetty.xml depends-on resolves

The BrokerXmlConfigStartTest loads all activemq-*.xml sample configs
which import jetty.xml. Since jetty.xml now has depends-on="broker" on
the invokeStart bean, the sample configs need a matching bean id.

Author: jbonofre

assembly/src/release/examples/conf/activemq-demo.xml

@@ -47,7 +47,7 @@
           - Change the brokerName attribute to something unique
     -->
 
-    <broker xmlns="http://activemq.apache.org/schema/core" brokerName="amq-broker" useJmx="true">
+    <broker xmlns="http://activemq.apache.org/schema/core" brokerName="amq-broker" useJmx="true" id="broker">
 
         <!--
             Examples of destination-specific policies using destination

assembly/src/release/examples/conf/activemq-security.xml

@@ -63,7 +63,7 @@
   </bean> 
   -->
 
-  <broker useJmx="true" persistent="false" xmlns="http://activemq.apache.org/schema/core" >
+  <broker useJmx="true" persistent="false" xmlns="http://activemq.apache.org/schema/core" id="broker">
 
     <managementContext>
         <managementContext createConnector="true">

assembly/src/release/examples/conf/activemq-stomp.xml

@@ -44,7 +44,7 @@
     <!--
         The <broker> element is used to configure the ActiveMQ broker.
     -->
-    <broker xmlns="http://activemq.apache.org/schema/core" brokerName="localhost" dataDirectory="${activemq.data}">
+    <broker xmlns="http://activemq.apache.org/schema/core" brokerName="localhost" dataDirectory="${activemq.data}" id="broker">
 
         <!--
             For better performances use VM cursor and small memory limit.