ISPN-4490 Members can miss the rebalance cancellation on coordinator change

Simulate the rebalance cancellation in StateTransferManagerImpl.
ISPN-4496 EncryptProtocolIT shouldn't check passwords via JMX
Replace ignore tests with empty test to avoid false alarms
ISPN-1951 Use MERGE3 in the default UDP configuration

TEST_PING needed some changes, as MERGE3 doesn't trigger Discovery.findMembers()
Smaller timer pool and queue.
Still causes lots of failures.