README documentation updates

Change-Id: Iba0de05caea7a1f0a8055a6139ad3ecaaaa662cd
Tighten up security group port settings for broker and node.

Separate security groups were created for broker and node hosts.
Firewall rules follow documentation:
https://access.redhat.com/site/documentation/en-US/OpenShift_Enterprise\
/2/html/Deployment_Guide/Network_Access.html

Change-Id: If54f9b636e13679372bd566c8cc8dc6a08e4c7d2
Fix parameter constraints syntax

The server flavor constraints were removed since custom flavors
may be defined that are outside the list of default flavors.

Change-Id: Ifa3d5791257a60a2462cdd4d0d5b53a6721bd50e