Reduce DNS lookups for the statsd domain

[elukey]

The sendto socket call is very flexible but it currently
issue a DNS lookup for the statsd domain for every
metric in the for loop to push. This change ensures that
only one lookup is performed for each batch of metrics
to send. It is particularly useful when logster runs
every minute and the number of metrics to push is very high.

Issue: #103

[benburry]

Thanks for your PR. Could you make the same change (resolve name -> ip before socket connect) to the other output module that follow this pattern, graphite, so that we can maintain consistent behaviour across them?

[elukey]

I think that the graphite module uses a different pattern, namely s.connect((host[0], int(host[1]))) before the loop and then s.sendall (that afaict it should not generate a DNS query). The statsd module creates a socket + sendto() for each iteration.

[benburry]

So it does. Thanks!