Adapt to Keystone changes: use member instead of Member

Keystone now provides "member" by default.
It should not be a problem for upgrades when the configuration
is the default one, because Keystone is case-preserving and
Member and member are the considered the same:
https://docs.openstack.org/keystone/latest/admin/identity-case-insensitive.html

Change-Id: I3bd72631d57546dcf8b887833539fe3ccaac4e47

devstack/upgrade/resources.sh

@@ -59,7 +59,7 @@ function create_user {
     resource_save sahara user_id $id
 
     # Workaround for bug: https://bugs.launchpad.net/keystone/+bug/1662911
-    openstack role add Member --user $id --project $project_id
+    openstack role add member --user $id --project $project_id
 }
 
 function create_keypair {

doc/source/admin/advanced-configuration-guide.rst

@@ -490,7 +490,7 @@ access. Please see the :keystone-doc:`Keystone documentation
 With the domain created, sahara's configuration file should be updated to
 include the new domain name and any potential roles that will be needed. For
 this example let's assume that the name of the proxy domain is
-``sahara_proxy`` and the roles needed by proxy users will be ``Member`` and
+``sahara_proxy`` and the roles needed by proxy users will be ``member`` and
 ``SwiftUser``.
 
 .. sourcecode:: cfg
@@ -498,7 +498,7 @@ this example let's assume that the name of the proxy domain is
     [DEFAULT]
     use_domain_for_proxy_users=true
     proxy_user_domain_name=sahara_proxy
-    proxy_user_role_names=Member,SwiftUser
+    proxy_user_role_names=member,SwiftUser
 
 A note on the use of roles. In the context of the proxy user, any roles
 specified here are roles intended to be delegated to the proxy user from the

releasenotes/notes/proxy-user-lowercase-f116f7b7e89274cb.yaml

@@ -0,0 +1,6 @@
+---
+upgrade:
+  - |
+    The default proxy role for Swift is now member instead of Member.
+    Keystone now creates the former by default,
+    even if the latter is recognized to be the same (case preserving).

sahara/utils/proxy.py

@@ -47,7 +47,7 @@ opts = [
                help='The domain Sahara will use to create new proxy users '
                     'for Swift object access.'),
     cfg.ListOpt('proxy_user_role_names',
-                default=['Member'],
+                default=['member'],
                 help='A list of the role names that the proxy user should '
                      'assume through trust for Swift object access.')
 ]