Fixes to 5.0 release notes

* Savanna renamed to Sahara
* 'Highly Available architecture can run with one controller' section
  was removed, along with information about controller nodes scale up
  due to unresolved Related-Bug #1312627
* Network verification can be started after deployment of Neutron
  enabled environment.
* We have network verification and validation, verification is
  performed actively by issuing udp frames or listening for dhcp
  replies, while validation is static mechanism to ensure that there
  no collisions in networking configuration
* 'deployment' replaced to 'provisioning' when we talk about OS
  bootstrapping
* RabbitMQ was temporarily issue and release-notes tag was put there
  likely by mistake
* ... few more minor fixes

Change-Id: If9d32d04b85fd34716fee40f5eafb59bc1ee673e
Merge "Fixes to 5.0 release notes"