Bug 1041565 - Setting for toggling pseudolocales

https://bugzilla.mozilla.org/show_bug.cgi?id=1041565
I see promising results with `client.scope({ searchTimeout: 50 });` which allows `waitForElementToDisappear` to fail quickly.

I think I'll stick to it, then. [Under the hood](https://github.com/mozilla-b2g/marionette-helper/blob/5065c64179cb0f2f6525770508c827e713664e36/index.js#L167), it does a regular `findElement` in a `try-catch` block, which seems to be the only way to get the reference to the element anyways.