[WORKER] Fix session persistence and health checks

1. Cookies were not being used properly
2. TCP connections had no sense of persistence
3. No health checks were performed on backend nodes,
   now 30 second TCP healthchecks are performed
4. maxconn increased after 503 concerns in heavy load
5. set redispatch for sessions stuck on dead nodes and last try
   of connection timeouts
6. Increase timeout in case web server has a slow application
7. enable forwardfor for people using things like geoip

Change-Id: Ia6b4890aea1e452d5cd9f94d9e7b975f6bf39076
Merge "[WORKER] Fix session persistence and health checks"