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
(cherry picked from commit 77131053d3d767887649a74a446aa081c8a67c80)
Merge "Fixes to 5.0 release notes" into stable/5.0