Enhance logging of test to see if issue #4237 is still occuring.

I ran this test over 20k times on my local machine. After a single failure I never see it failing again (Heisenbug). I stepped through the code, didn't see anything which looks obviously wrong. I would recommend to merge this enhanced logging to have better data if this test fails again.

The failure occured in 3.x maintenance branch, but I would recommend to merge the enhanced logging in 3.4, too. At least the method HazelcastTestSupport.assertEqualsStringFormat() should be quite helpful for the future.