Bug 918970 - display existing thread when sending a sms from contact app

old PR : https://github.com/mozilla-b2g/gaia/pull/16216

Contacts.findByPhoneNumber was not mocked, so the real function was called and relied on test/unit/mock_contact.js
We were having Pepito O'Hare each time, but if you look at the old code, we put the name of the contact we find with the number we have in parameter. This seems quite odd to me : we are mixing data sources, in a sense. Well normally, this should not be an issue, assuming findByPhoneNumber does his job well.

So the stub was just useless, but things were working because of contact mock test conf. I prefer to rely on a good mocking. After all, we are unit testing here (and I added tests concerning contacts).