fix misleading message w/ --set_low_power
fix misleading message w/ --set_low_power

Summary:
copypasta when adding this option lead to a misleading
message. Noticed when using to test power setting workaround.

Differential Revision: D4348244

fbshipit-source-id: 9e27b7c327821d237aed8e20a1bc008aef341119

peterlei/fboss,peterlei/fboss,peterlei/fboss,peterlei/fboss