test: make the vm timeout escape tests more lenient

Previously the tests required that Node.js finish the initialization of the watchdog thread and fires the timeout within 100ms, which can be difficult on certain systems under load. This patch relaxes the requirement to 2000ms. If there is a bug and the timeout can actually be escaped, raising the timeout to 2000ms would not make a difference anyway.

Refs: https://github.com/nodejs/reliability/issues/333 Refs: https://github.com/nodejs/reliability/issues/361