Init
JUnit ClassRule which initializes the AOSP CalendarProvider.
It seems that the calendar provider unfortunately forgets the very first requests when it is used the very first time, maybe by some wrongly synchronized database initialization. So things like querying the instances fails in this case.
So this rule is needed to allow tests which need the calendar provider to succeed even when the calendar provider is used the very first time (especially in CI tests / a fresh emulator).