fs: sequential/test-fs-watch timeout on OS X

[silverwind]

This fails every time here. I first put it off as a local issue, but now it comes up in some CI runs too:

=== release test-fs-watch ===
Path: sequential/test-fs-watch
Command: out/Release/iojs /Users/iojs/build/workspace/iojs+any-pr+multi/nodes/osx1010/test/sequential/test-fs-watch.js
--- TIMEOUT ---

https://jenkins-iojs.nodesource.com/view/iojs/job/iojs+any-pr+multi/378/nodes=osx1010/

[silverwind]

Correction: It fails around 80-90% of all runs on my machine (2013 MBA), investigating.

[silverwind]

So this seems to be write timeout related. Changing the write timeouts from 10ms to 15ms seems to make the failures go away.

The last timeout change is here: c5ed96a

@bnoordhuis would you agree with increasing these timeouts to like 20ms to reduce test flakiness?

[silverwind]

continued in #1275.