Support a flag for setting Keystone Token backend

Fixes LP# 1073274

Change-Id: Ib4373a4a4d31e440e40f977f8f7ffa312f2d97be
diff --git a/lib/keystone b/lib/keystone
index 7a70cc4..5714670 100644
--- a/lib/keystone
+++ b/lib/keystone
@@ -39,6 +39,9 @@
 KEYSTONE_CATALOG_BACKEND=${KEYSTONE_CATALOG_BACKEND:-sql}
 KEYSTONE_CATALOG=$KEYSTONE_CONF_DIR/default_catalog.templates
 
+# Select the backend for Tokens
+KEYSTONE_TOKEN_BACKEND=${KEYSTONE_TOKEN_BACKEND:-sql}
+
 # Select Keystone's token format
 # Choose from 'UUID' and 'PKI'
 KEYSTONE_TOKEN_FORMAT=${KEYSTONE_TOKEN_FORMAT:-PKI}
@@ -108,6 +111,12 @@
     # Append the S3 bits
     iniset $KEYSTONE_CONF filter:s3_extension paste.filter_factory "keystone.contrib.s3:S3Extension.factory"
 
+    if [[ "$KEYSTONE_TOKEN_BACKEND" = "sql" ]]; then
+        iniset $KEYSTONE_CONF token driver keystone.token.backends.sql.Token
+    else
+        iniset $KEYSTONE_CONF token driver keystone.token.backends.kvs.Token
+    fi
+
     if [[ "$KEYSTONE_CATALOG_BACKEND" = "sql" ]]; then
         # Configure ``keystone.conf`` to use sql
         iniset $KEYSTONE_CONF catalog driver keystone.catalog.backends.sql.Catalog