Improve error handling when service config isn't found in redis

[cjus]

Consider a better way of addressing this exception.

Error: Invalid service stored config
    at _getConfig.then (/usr/src/app/node_modules/hydra/index.js:201:30)
    at tryCatcher (/usr/src/app/node_modules/bluebird/js/release/util.js:16:23)
    at Promise._settlePromiseFromHandler (/usr/src/app/node_modules/bluebird/js/release/promise.js:512:31)
    at Promise._settlePromise (/usr/src/app/node_modules/bluebird/js/release/promise.js:569:18)
    at Promise._settlePromise0 (/usr/src/app/node_modules/bluebird/js/release/promise.js:614:10)
    at Promise._settlePromises (/usr/src/app/node_modules/bluebird/js/release/promise.js:693:18)
    at Async._drainQueue (/usr/src/app/node_modules/bluebird/js/release/async.js:133:16)
    at Async._drainQueues (/usr/src/app/node_modules/bluebird/js/release/async.js:143:10)
    at Immediate.Async.drainQueues (/usr/src/app/node_modules/bluebird/js/release/async.js:17:14)
    at runCallback (timers.js:672:20)
    at tryOnImmediate (timers.js:645:5)
    at processImmediate [as _immediateCallback] (timers.js:617:5)