devstack: try to emulate `sp-openstack groups cinder,nova,glance`

Change-Id: I3065dcff5f40e9fcbffd4e2984b1890911bd870a
diff --git a/roles/sp-openstack-integration-groups/README.rst b/roles/sp-openstack-integration-groups/README.rst
new file mode 100644
index 0000000..0561f3d
--- /dev/null
+++ b/roles/sp-openstack-integration-groups/README.rst
@@ -0,0 +1,2 @@
+Add the `spopenstack` group and add the (still non-existent)
+`cinder`, `nova`, and `glance` user accounts to it.