Clean up TimeUnit dependencies

The time unit that is set in StartJVMMonitorStage is shared between the
LocalJmxMonitor and ClusterTimeSeriesReport classes. This commit
includes the following changes:

	Remove the static access for the TimeUnit in LocalJmxMonitor
	Use the public getter in LocalSystemMonitorChart to get the TimeUnit
	Add the TimeUnit to the constructor of ClusterTimeSeriesReport