Bug 1086676 - Add a test to check notification when you miss a call from...

... a known contact
Let's not check for the missed call notification this way. We should better wait for notification toaster to appear & dissapear, then expand notification bar, in order to see the missed call. You can see an example in [test_system_notification_bar.py][link]
[link] https://github.com/mozilla-b2g/gaia/blob/master/tests/python/gaia-ui-tests/gaiatest/tests/functional/system/test_system_notification_bar.py#L22