Update unit tests to use new socket schema

I forgot to update Gauge and EventMetricProducer unit test files to use
the new socket schema.

The EventMetric tests were also incomplete so I added test code to
output the dump report and check its contents.

Test: bit statsd_test:*
Bug: 149590301 && 110561136

Change-Id: I685688285d9890cf7c5bd3ffc43f13cbbb8f93de