Convert test suite to use sinon assertions

Is this a feature request or a bug?

feature

What is the current behavior?

In the test suite we do things like this to check that stub objects are called correctly:

assert.ok(addonReload.called);
assert.equal(addonReload.firstCall.args[0].addonId,
  tempInstallResult.addon.id);

What is the expected or desired behavior?

It works but the failure messages could be better. Let's switch all of this code to sinon assertions instead.

The above test would be rewritten as:

sinon.assert.calledWith(
  addonReload, sinon.match({addonId: tempInstallResult.addon.id})
);