test: fix test-domain-exit-dispose-again

test-domain-exit-dispose-again had been written for node v0.10.x, and was using the fact that callbacks scheduled with process.nextTick wouldn't run if the domain attached to it was disposed.

This is not longer the case, and as a result the test would not catch any regression: it would always pass.

This change rewrites that test to check that the current domain is cleared properly when processing the rest of the timers list if a timer's callback throws an error. This makes the test fail without the original fix, and pass with the original fix, as expected.