ENG-409: wired quickSize and quickClear into CacheSamplerImpl

git-svn-id: http://svn.terracotta.org/svn/ehcache@8344 b9324663-ca0f-0410-8574-be9b3887307d
MNK-5685 Use a retryAssert for greaterThan assert and give them more time to succeed

git-svn-id: http://svn.terracotta.org/svn/ehcache@8345 b9324663-ca0f-0410-8574-be9b3887307d
MNK-5596 Use executor service to be able to get to exceptions inside callable

git-svn-id: http://svn.terracotta.org/svn/ehcache@8346 b9324663-ca0f-0410-8574-be9b3887307d