AbstractFullNodeTest.setUp(): Fix IllegalStateException

Would happen in NodeStarter.globalTestInit() because the setUp() was
being executed twice per VM, but globalTestInit() must only be called
once for each VM.

java.lang.IllegalStateException
	at freenet.node.NodeStarter.globalTestInit(NodeStarter.java:306)
	at plugins.WebOfTrust.AbstractFullNodeTest.setUp(
		AbstractFullNodeTest.java:88)
AbstractFullNode: Prevent child classes from overriding stuff

- Rename setUp() to setUpNode() and tearDown() to tearDownNode() as
JUnit4 allows arbitrary function names because it depends on "@Before" /
"@After" annotations instead of parsing the function names.
- Make all functions final
SubscriptionManagerFCPTest: Fix JUnit4 complaining about no tests

The class was originally a JUnit3 class so it had "test*()" functions
instead of "@Test" annotations. Therefore, this commit adds the
annotations.