Add configure-devstack task for devstack gate

This patch adds 'configure-devstack' task to enable CORS headers in
keystone before functional-test are run.
No 'ini' library was used as I didn't find any supporting section
syntax "[[post-config|$KEYSTONE_CONF]]"

Change-Id: I7f335bbba3a768387a7d77916df019ba46e5519f

configure-devstack.js

@@ -0,0 +1,17 @@
+/*eslint no-process-env: "off" */
+import fs from 'fs';
+import karma from 'karma/lib/config';
+import path from 'path';
+
+function getDevstackConfig() {
+  const karmaConfig = karma.parseConfig(path.resolve('./karma.conf.js'));
+  return "[[post-config|$KEYSTONE_CONF]]\n" +
+    "[cors]\n" +
+    "allowed_origin=http://localhost:" + karmaConfig.port + "\n";
+}
+
+fs.appendFile(process.env.BASE + '/new/devstack/local.conf', getDevstackConfig(), (err) => {
+  if (err) {
+    throw err;
+  }
+});

package.json

@@ -4,6 +4,7 @@
   "description": "JavaScript API library for OpenStack.",
   "main": "dist/index.js",
   "scripts": {
+    "configure-devstack": "babel-node ./configure-devstack.js",
     "test": "npm run test:node; npm run test:browser",
     "test:node": "istanbul cover jasmine JASMINE_CONFIG_PATH=test/unit/jasmine.json",
     "test:browser": "karma start",