qunit: Disable sinonjs-ie as it breaks the clock sandbox

The ie fixes file assumes running in the global scope. Since it
runs locally in our environment, it ends up destroying its
references to e.g. the Date object.

Then when calling sandbox.useFakeTimers, the Date constructor
will yield an object with no methods and tests will fail at a
random point when e.g. trying to access date.getTime().

* Remove 'clock' from the sinon properties we inject into the
  test context. We use the sandbox instead (just like for server).

  This also fixes a shadow clash with the tests that stored the
  clock instance in `this.clock`.

Change-Id: I6085bccf5038e4751da48ee765fe81560f58c6e8
Merge "qunit: Disable sinonjs-ie as it breaks the clock sandbox"