Bug 1096920 - Add test to delete entire call log when it has several cal...

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I think we have too much UI steps in the setUp. I would suggest to create an `insertCall` function in the `gaia_data_layer` atom and to add some logs [like in here](https://github.com/mozilla-b2g/gaia/blob/master/apps/communications/dialer/test/unit/call_log_db_test.js#L120). If we do that, we would be able to run this test on b2g-desktop. What do you guys think?