Passing Client IP across Multiple Proxies
If the load balancer is inserting the client IP address in a header called ClientIP, mod_proxy should pass that on to the Tomcat sever without any special configuration. Try configuring the Tomcat RemoteIpValve to look for ClientIP instead of X-Forwarded-For. e.g.
<Valve className="org.apache.catalina.valves.RemoteIpValve"
remoteIpHeader="ClientIP"
protocolHeaderHttpsValue="https" />