Fix the tests: Unhandled rejection Error: spy was never called

Nobody has claimed this yet.

Aren't the tests broken even though travis shows it as passing or am I misunderstanding the travis logs for the recent pull requests?

https://travis-ci.org/matrix-org/matrix-js-sdk/builds/436211876#L8862
```
394 passing (11s)
13 pending
Saving device tracking data at token null
got keys for @test1:sw1v.org: {}
Completed key download for @test1:sw1v.org
Starting key download for [ '@test1:sw1v.org' ]
Another update in the queue for @test1:sw1v.org - not marking up-to-date
Creating new devicelist to simulate app reload
Unhandled rejection Error: spy was never called with [ [ '@test1:sw1v.org' ], {} ]
at assert (/home/travis/build/matrix-org/matrix-js-sdk/node_modules/expect/lib/assert.js:29:9)
at Expectation.toHaveBeenCalledWith (/home/travis/build/matrix-org/matrix-js-sdk/node_modules/expect/lib/Expectation.js:333:28)
at /home/travis/build/matrix-org/matrix-js-sdk/spec/unit/crypto/DeviceList.spec.js:138:33
at tryCatcher (/home/travis/build/matrix-org/matrix-js-sdk/node_modules/bluebird/js/release/util.js:16:23)
at Promise._settlePromiseFromHandler (/home/travis/build/matrix-org/matrix-js-sdk/node_modules/bluebird/js/release/promise.js:512:31)
at Promise._settlePromise (/home/travis/build/matrix-org/matrix-js-sdk/node_modules/bluebird/js/release/promise.js:569:18)
at Promise._settlePromise0 (/home/travis/build/matrix-org/matrix-js-sdk/node_modules/bluebird/js/release/promise.js:614:10)
at Promise._settlePromises (/home/travis/build/matrix-org/matrix-js-sdk/node_modules/bluebird/js/release/promise.js:694:18)
at _drainQueueStep (/home/travis/build/matrix-org/matrix-js-sdk/node_modules/bluebird/js/release/async.js:138:12)
at _drainQueue (/home/travis/build/matrix-org/matrix-js-sdk/node_modules/bluebird/js/release/async.js:131:9)
at Async._drainQueues (/home/travis/build/matrix-org/matrix-js-sdk/node_modules/bluebird/js/release/async.js:147:5)
at Immediate.Async.drainQueues [as _onImmediate] (/home/travis/build/matrix-org/matrix-js-sdk/node_modules/bluebird/js/release/async.js:17:14)
at runCallback (timers.js:694:18)
at tryOnImmediate (timers.js:665:5)
at processImmediate (timers.js:647:5)
```

Start with spec/unit/crypto/DeviceList.spec.js at line 138 and compare the failure in the linked Travis build with the test runner's reported result. Trace how the asynchronous assertion is handled and confirm the suite reports the failure correctly; done means the test outcome is no longer silently shown as passing.

Written by the indexing model from the issue text.