cosmetic: tests/power: remove unused var "ret"
cosmetic: tests/power: remove unused var "ret"

remove unused variable "ret" in unit test "power"

Change-Id: Ied484e3e2d3006eb0f03516ceaed3e0e802d51e4

osmocom/osmo-bts,osmocom/osmo-bts,osmocom/osmo-bts