Revise functional testing README file

Clarifies the location of clouds.yaml for functional testing.

Change-Id: Ib0b8e84579bca72e791229752df14542358e21b7

glanceclient/tests/functional/README.rst

@@ -27,10 +27,13 @@ Functional Test Guidelines
 
 The functional tests require:
 
-1) A working Glance/Keystone installation (eg devstack)
+1) A working Glance/Keystone installation (for example, devstack)
 2) A yaml file containing valid credentials
 
-If you are using devstack a yaml file will have been created for you.
+If you are using devstack, a yaml file will have been created for you
+with the name /etc/openstack/clouds.yaml.  The test code knows where
+to find it, so if you're using devstack, you don't need to do anything
+else.
 
 If you are not using devstack you should create a yaml file
 with the following format:
@@ -39,15 +42,21 @@ with the following format:
    devstack-admin:
      auth:
        auth_url: http://10.0.0.1:35357/v2.0
-
        password: example
-
+       project_domain_id: default
        project_name: admin
-
+       user_domain_id: default
        username: admin
-
      identity_api_version: '2.0'
-
      region_name: RegionOne
 
-and copy it to ~/.config/openstack/clouds.yaml
+The tests will look for a file named 'clouds.yaml' in the
+following locations (in this order, first found wins):
+
+* current directory
+* ~/.config/openstack
+* /etc/openstack
+
+You may also set the environment variable OS_CLIENT_CONFIG_FILE
+to the absolute pathname of a file and that location will be
+inserted at the front of the search list.