Logout fails the api call as it doesn't pass in access_token

[raymondfeng]

Here is the error response from the api call:

{"error":{"name":"Error","status":500,"message":"could not find accessToken","stack":"Error: could not find accessToken\n    at /home/raymond/strong-subscription-admin/node_modules/loopback/common/models/user.js:278:12\n    at /home/raymond/strong-subscription-admin/node_modules/loopback-datasource-juggler/lib/dao.js:1407:62\n    at allCb (/home/raymond/strong-subscription-admin/node_modules/loopback-datasource-juggler/lib/dao.js:1339:7)\n    at /home/raymond/strong-subscription-admin/node_modules/loopback-connector-mongodb/lib/mongodb.js:713:9\n    at handleCallback (/home/raymond/strong-subscription-admin/node_modules/loopback-connector-mongodb/node_modules/mongodb/lib/utils.js:95:12)\n    at /home/raymond/strong-subscription-admin/node_modules/loopback-connector-mongodb/node_modules/mongodb/lib/cursor.js:590:16\n    at handleCallback (/home/raymond/strong-subscription-admin/node_modules/loopback-connector-mongodb/node_modules/mongodb/node_modules/mongodb-core/lib/cursor.js:234:5)\n    at setCursorNotified (/home/raymond/strong-subscription-admin/node_modules/loopback-connector-mongodb/node_modules/mongodb/node_modules/mongodb-core/lib/cursor.js:434:3)\n    at /home/raymond/strong-subscription-admin/node_modules/loopback-connector-mongodb/node_modules/mongodb/node_modules/mongodb-core/lib/cursor.js:535:16\n    at queryCallback (/home/raymond/strong-subscription-admin/node_modules/loopback-connector-mongodb/node_modules/mongodb/node_modules/mongodb-core/lib/cursor.js:215:5)"}}

[ritch]

I've added a better error message to loopback. We still need to fix the case where it is not passed in from the original call though (in the browser).