CallOptions.timeout in `zone.execute' should be followed more precisely

[daiyip]

Code

console.time('timeout test');
zone.execute(() => { while (true) {} }, [], { timeout: 50})
    .catch((error) => {
        console.timeEnd('timeout test');
    });

Expected

timeout test: varies between 50 - 60ms

Actual

timeout test: around 50.00 ms