[FIXED JENKINS-16443] Document how to specify multiple servers for failover support

- The code has supported multiple redundant servers, but the help did not indicate the support

src/main/resources/hudson/security/LDAPSecurityRealm/config.jelly

@@ -24,7 +24,7 @@ THE SOFTWARE.
 
 <?jelly escape-by-default='true'?>
 <j:jelly xmlns:j="jelly:core" xmlns:st="jelly:stapler" xmlns:d="jelly:define" xmlns:l="/lib/layout" xmlns:t="/lib/hudson" xmlns:f="/lib/form">
-	<f:entry title="${%Server}" help="/help/security/ldap/server.html">
+	<f:entry title="${%Server}" help="/plugin/ldap/help-server.html">
 	  <f:textbox name="ldap.server" value="${instance.server}"
             checkUrl="'${rootURL}/securityRealms/LDAPSecurityRealm/serverCheck?field=server&amp;server='+encodeURIComponent(this.value)+'&amp;managerDN='+encodeURIComponent(this.form.elements['ldap.managerDN'].value)+'&amp;managerPassword='+encodeURIComponent(this.form.elements['ldap.managerPassword'].value)"/>
 	</f:entry>

src/main/webapp/help-server.html

@@ -0,0 +1,13 @@
+<div>
+    Specify the name of the LDAP server host name(s) (like <tt>ldap.sun.com</tt>).
+    If your LDAP server uses a port other than 389 (which is the standard for LDAP),
+    you can also append a port number here, like <tt>ldap.acme.org:1389</tt>.
+    To connect to LDAP over SSL (AKA LDAPS), specify it with the <tt>ldaps://</tt> protocol,
+    like <tt>ldaps://ldap.acme.org</tt> or <tt>ldaps://ldap.acme.org:1636</tt> (if
+    the port is other than the default 636).
+    <br/>
+    Where there are multiple redundant servers separate them by spaces, if the first
+    named server is not available then requests will be attempted by each of the
+    named servers in order. NOTE: This is to support LDAP server fail-over, once an any
+    answer has been received from a server, that answer is taken as definitive
+</div>