Document "use_rdo"

README.md

@@ -267,6 +267,7 @@ Attributes
 * `node['setup']['openstack_rc_group']` - The owner of the credentials script.  Defaults to 'root'.
 * `node['setup']['openstack_try_pip']` - If true, try to install clients from Pypy, using pip.  Defaults to true.
 * `node['setup']['openstack_try_distro']` - If true, try to install clients from the distro's repository.  Defaults to false.
+* `node['setup']['openstack_use_rdo']` - If true, try to use the Fedora "RDO" repository in preference to the distro's.  Defaults to false.
 
 If the 'openstack_tenant_name' attribute is defined and non-empty, then a 
 credentials file will be generated containing the details.
@@ -278,6 +279,13 @@ Precise, there is no Swift client in the package repo, and the Pypy version
 of the Swift client in incompatible with the Ubuntu precise version of the
 Keystone client.) 
 
+The RDO repos are maintained by the RDO community 
+(http://openstack.redhat.com/Main_Page) and aim to provide up-to-date 
+builds of OpenStack related "stuff" for Fedora and RHEL-based systems.
+Unfortunately, they don't provide complete coverage, so the 'openstack_clients'
+recipe is designed to try to use an RDO repo if it exists, and fall back to
+the standard distro (with a WARN log message).
+
 The credentials script is created with permissions `0550`, and defaults to 
 having "root:root" ownership.