As per the 2.4-to-2.5 migration guide using UntypedAbstractActor
UntypedActor is our cheapest migration option. This requires
updating MeteringBehavior to integrate with Receive.
Change-Id: I692f723dffc966bb7e117124b7a0cd714572ab4f Signed-off-by: Robert Varga <robert.varga@pantheon.tech>