Support -Ddebug for clustering testsuite

This has been broken for a while now; there are still traces of properties such as as.debug.port.node3 but never set.

• What could to be done is to pick up -Ddebug and setup debug lines for each server with specific ports, i.e. ports.
• However, suspend=y need to be used reasonably, since this makes for an arduous debugging session.
• Probably one server could be picked up for debugging.
• Moreover, timeouts should probably be heavily increased not to timeout very quickly.