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)
The suggestion to put concrete examples of probability is great. I was considering removing the comment altogether after your comment above about the birthday paradox, but this would be very useful to add.