Bug 1070731 - [sms] unit test refactoring for new version chai.assert api

test_agent used very old version chai library version=0.5.3
in the current version=1.9.1 deepEqual take prototype into consideration

apps/sms/test/unit/localization_helper_test.js - plain structure
Probably the easiest (not ideal though) option would be to move ```if``` into ```assertChange``` itself. For the _1st_ ```assertChange``` it would be:
```
function assertChange(format, doNotFormat) {
  // In case of time format change date-only elements aren't updated
  if (doNotFormat) {
    assert.equal(
      node.textContent, '', 'Date-only elements should not be updated'
    );
  } else {
    assert.equal(
      node.textContent,
      Utils.date.format.localeFormat(new Date(timestamp), format)
    );
  }

  assert.isFalse(node.hasAttribute('data-l10n-id'));
  assert.isFalse(node.hasAttribute('data-l10n-args'));
}
```
and instead of ```if``` branch with ```assert.throws``` call it like:
```
assertChange(node.dataset.l10nDateFormat, forceUpdateMethod());
```

The same is for the _2nd_ ```assertChange```:
```
function assertChange(format, doNotFormat) {
  var l10nAttributes = navigator.mozL10n.getAttributes(node);
  // In case of time format change date-only elements aren't updated
  if (doNotFormat) {
    assert.deepEqual(l10nAttributes.args, {
      data: 'custom'
    }, 'Date-only elements should not be updated');
  } else {
    assert.deepEqual(l10nAttributes.args, {
      data: 'custom',
      date: Utils.date.format.localeFormat(new Date(timestamp), format)
    });
  }

  assert.equal(l10nAttributes.id, 'custom');
  assert.equal(node.textContent, 'not-changed-content');
}
```