[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
[API] Don't set an ERROR'd device back OFFLINE on delete

Change-Id: I6974b7f1466f2842baaffea2b2e93e8edc5e41bf