title: p:watermark clears on updating Component even if there is no value
body: <p>I'm using Primefaces <code>p:watermark</code> on a <code>p:inputText</code>. Its working fine.<br>
  When ever I update the component its loosing watermark,even when there is no content inside the <code>p:inputText</code></p>
  
  <pre><code>&lt;h:form id="reg_frm"&gt;
     &lt;p:inputText id="name" value="#{user.name}"/&gt;
     &lt;p:watermark value="your name" for="name" id="name_watermark" /&gt;
  
     &lt;p:selectOneMenu value="#{user.drpvalue}"&gt;
        &lt;f:selectItem itemLabel="One" itemValue="1"/&gt;
        &lt;f:selectItem itemLabel="two" itemValue="2"/&gt;
        &lt;f:selectItem itemLabel="three" itemValue="3"/&gt;
        &lt;f:selectItem itemLabel="four" itemValue="4"/&gt;
        &lt;p:ajax event="change" update="name name_watermark"/&gt;
     &lt;/p:selectOneMenu&gt;
  
  &lt;/h:form&gt;
  </code></pre>
  
  <blockquote>
    <p>How do I retain the Watermark when there is no content in the
    <code>p:inputText</code> after update?</p>
  </blockquote>
  
  <p><em>Note: Primefaces version - 3.5</em></p>