Add tests for filter notification ordering

There was a bug in the Java agent with regards to agent teardown:
upon disconnection, the list of tracked events was cleared but no
corresponding filter change notifications were sent! This could leave
some event rules dangling, and future listeners would get incorrectly
notified that these events were enabled while they were not.

Add some tests to cover for this use case.

Signed-off-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>