origfn

Hi, I've this error on graceful queue shutdown on version 0.10.5:

origfn is not a function
Apr 27 08:29:59 test-air-alvieromartini app/web.2: 15:29:58 web-app-0 STACK:
Apr 27 08:29:59 test-air-alvieromartini app/web.2: 15:29:58 web-app-0 TypeError: origFn is not a function
Apr 27 08:29:59 test-air-alvieromartini app/web.2: 15:29:58 web-app-0 at Queue.shutdown (/app/node_modules/kue/lib/kue.js:423:5)
Apr 27 08:29:59 test-air-alvieromartini app/web.2: 15:29:58 web-app-0 at process. (/app/workers/queue.js:14:18)
Apr 27 08:29:59 test-air-alvieromartini app/web.2: 15:29:58 web-app-0 at process.g (events.js:260:16)
Apr 27 08:29:59 test-air-alvieromartini app/web.2: 15:29:58 web-app-0 at emitNone (events.js:72:20)
Apr 27 08:29:59 test-air-alvieromartini app/web.2: 15:29:58 web-app-0 at process.emit (events.js:166:7)
Apr 27 08:29:59 test-air-alvieromartini app/web.2: 15:29:58 web-app-0 at Signal.wrap.onsignal (node.js:804:46)

Seems to be a regression to [https://github.com/Automattic/kue/issues/606](https://github.com/Automattic/kue/issues/606)

Start at Queue.shutdown in lib/kue.js:423 and inspect the caller shown at /app/workers/queue.js:14. Compare the regression with issue #606 and reproduce graceful queue shutdown on version 0.10.5. Done means shutdown completes without the “origFn is not a function” TypeError.

Written by the indexing model from the issue text.