Set and restore default timezone in DateUtilsTest

Previously, the tests assumed a GMT timezone without ever setting it.
Now we set the timezone to GMT on setup and restore the original
timezone on teardown.

Change-Id: Ia168335eac28f33c094581af2437ac635cb38bd9
Fixes: 64149941
Test: bit FrameworksCoreTests:android.text.format.DateUtilsTest (with non-GMT timezone)
1 file changed