tests/eas/rfc: Only use the energy meter if the platform supports it
Created by: JaviMerino
EnergyMeter.getInstance() returns None if there is no energy meter for the platform. Therefore, env.emeter is None for platforms that don't have an energy meter and rfc.py fails with an AttributeError when it tries to do things like cls.env.emeter.reset()
Check that emeter is not None before calling any of its methods.