Bug 838993 - Temporarily disable failing tests r=julienw

These unit tests are currently failing and have been temporarily
disabled as per Bug 838993. They should be fixed and re-enabled
as soon as possible.

The following bugs track the process of re-enabling:

- Bug 838622 - [Dialer] USSD unit tests are failing
- Bug 840489 - [calendar] Fix failing unit tests
- Bug 840493 - [gallery] Fix failing unit tests
- Bug 840495 - [keyboard] Fix failing unit tests
- Bug 840497 - [sms] Fix failing unit tests
- Bug 840500 - [system] Fix failing unit tests
- Bug 841045 - [contacts] Fix failing unit tests
(cherry picked from commit 1c853f124b869218c88a1452377fd9c1dedb23bd)

Conflicts:

	apps/calendar/test/unit/views/month_test.js
(cherry picked from commit 96dffe8cdb68205e8475a8bd10f455c5a7ccfaff)