test: work around node bug, use setImmediate()
test: work around node bug, use setImmediate()

process.nextTick() in some Node.js prereleases seems to stall
after about ~194 calls.

Since I'm using one of those prereleases, use setImmediate()
as a workaround.

PR-URL: https://github.com/bnoordhuis/node-unix-dgram/pull/50
Reviewed-By: Santiago Gimeno <3f17e29e343c4cf8809fb0970d81d6d8ee88d6b3@gmail.com>

bnoordhuis/node-unix-dgram,bnoordhuis/node-unix-dgram,bnoordhuis/node-unix-dgram