start the workers when we start
start the metrics workers; the metricsmanager should rely on a machine agent connection

sensible periods for the metric workers
only an environment manager can access the metrics api
added a machiner test and vars for cleanup and sender periods
bug fix in worker test
the periods for the metric workers should be const
Merge pull request #792 from mattyw/start-metric-workers

start the metric workers in the machiner

> Start the metric workers in the machiner

> Fixed the metricmanager api to only accept connections from a machine agent

> Sensible periods for the metric workers