Reset _writePos to zero.

This is a bug, we forgot to reset writePos
unref interval in packet-queue

The previous version of statsd-client would not keep
    a process open. This new version does.

To keep back compat we need to ensure that the statsd-client
    does not keep the process open.
Merge pull request #13 from uber/0.0.4-dns-recovery.bug-fixes

[DNS recovery]: Bug fixes