Remove the need for permission during tests

A call to ActivityManager was not faked for tests leading to a real
permission check. There's no need for this, so it have been fixed in the
service. Some other calls that can be faked have also been switched
over to the "injector" object.

Test: atest FrameworksTimeServicesTests
Bug: 182461754
Change-Id: Ic757932fee972d5ee360023a10f6616f36da271e