Improved PING and FD protocols for the testsuite

Create:

• INFINISPAN_TEST_PING: use thread locals to maintain cluster membership since all tests run in same JVM. This would make discovery rock solid and would make the testsuite more robust.
• INFINISPAN_TEST_FD: instead of relying on pings to check whether the node is there, attach a cache or cache manager listener to detect when a cache stops or fails and propagate that information back to the membership.