lisa.tests.base: Factor RTATestBundle.unscaled_utilization()
lisa.tests.base: Factor RTATestBundle.unscaled_utilization()

Uses PeriodicWload.unscaled_duty_cycle_pct() implementation to
deduplicate equivalent code.

ARM-software/lisa,credp/lisa,ARM-software/lisa,credp/lisa,credp/lisa,ARM-software/lisa,credp/lisa,ARM-software/lisa