Fix MW_STATSD_PORT to point to correct listener

The MW_STATSD_PORT value was referencing the carbon listener port instead of
the statsd listener port. These are not interchangeable as the two
services use different protocols. I changed the puppet variable names to
make this difference clear as well.

Bug: 62667
Change-Id: Ibda41273084f01f41062471afc999b1fd8fcc5b0