Add support for role and resource keystone backends

Keystone further broken apart the assignment backend into: role,
resource, and assignment. We should define the backends in the
config file and allow users to override the default by passing in
their own value.

Change-Id: Ieb22c428609d3db852814c7eceb77efa6bbde633
diff --git a/lib/keystone b/lib/keystone
index b4b7df9..0c2722c 100644
--- a/lib/keystone
+++ b/lib/keystone
@@ -68,6 +68,12 @@
 # Select the Assignment backend driver
 KEYSTONE_ASSIGNMENT_BACKEND=${KEYSTONE_ASSIGNMENT_BACKEND:-sql}
 
+# Select the Role backend driver
+KEYSTONE_ROLE_BACKEND=${KEYSTONE_ROLE_BACKEND:-sql}
+
+# Select the Resource backend driver
+KEYSTONE_RESOURCE_BACKEND=${KEYSTONE_RESOURCE_BACKEND:-sql}
+
 # Select Keystone's token provider (and format)
 # Choose from 'uuid', 'pki', 'pkiz', or 'fernet'
 KEYSTONE_TOKEN_FORMAT=${KEYSTONE_TOKEN_FORMAT:-}
@@ -209,6 +215,8 @@
 
     iniset $KEYSTONE_CONF identity driver "$KEYSTONE_IDENTITY_BACKEND"
     iniset $KEYSTONE_CONF assignment driver "$KEYSTONE_ASSIGNMENT_BACKEND"
+    iniset $KEYSTONE_CONF role driver "$KEYSTONE_ROLE_BACKEND"
+    iniset $KEYSTONE_CONF resource driver "$KEYSTONE_RESOURCE_BACKEND"
 
     iniset_rpc_backend keystone $KEYSTONE_CONF