Upgrade notes update for 11.1.8  (Please hold until EC11.1.8 ships)

* Document issues OC-11669 and OC-11670
* note the bump to EC 11.1.8. 
* Better explain how to monitor the system during an upgrade and what services are OK to be down.  
* Remove now unneeded patches for OC-11490 and OC-11382