Improvement on AtomicLongTest

Unit tests for IAtomicLong methods, instead of one huge testSimpleAtomicLong() method.
we have a function called 'randomString' in the HazelcastTestSupport class. 

So you get:
IAtomicLong a1 = hzInstance.getAtomicLong(randomString())

And I would not call the atomiclong a1. There is no a2 :) And normally variables with a number or not the best choice (sometimes they are). I would call it number or atomicNumber.