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)
>if the creation failed (log.warn), e.g. because a directory was not writable or disk is full

There is a third option where someone else creates the folder between our !exists() & mkdir() calls, so even in this case we can't be sure that the failure is due to io error.