Fix failing tests

  * brooklyn.util.ResourceUtilsTest.testGetResourceViaClasspathWithoutPrefix() fails on windows paths when OSGi is used
  * Explicitly wait for osgi framework shutdown before deleting the cache folder so all files are unlocked
  * LocationUsageTrackingTest.testUsageIncludesStartAndStopEvents - the test excludes the start and stop ms from the range of possible values
  * Temporary file and folder creation wasn't deterministic, resulting in unexpected exceptions
  * UsageResourceTest - guarantee the 1ms delay that the test assumes at specific points (can't use dates in the future)
have worked through the math.  it's the old "how many people in a room until there's a better than even chance two have the same birthday" problem.  suggest the comment on the `debug` explain this, that with random id of length 4 it's not unusual to have duplicates at the 2000 members mark.