Bug 872277 - Main localization is injected after other 'ready' callbacks. r=stas

Don't call ctx.localize in a 'ready' listener in the bindings.  ctx.localize
will bind a callback with _retr anyways and the change from bug 868677 [1] will
make it execute before other 'ready' listeners.

[1] https://github.com/l20n/l20n.js/commit/a89efbf159e0aed0709a6691424583accf6a21d4#L1L468