In the PowerUsageAdvanced screen the text showing whether your time
remaining information is enhanced or not should not show when the
device is plugged in. This CL fixes a bug in that logic that would
show the text when it wasn't supposed to.
Test: robotests still pass, manual verification
Bug: 63176050
Change-Id: I33fb31671cd9c29aed20483301e51ae1ded1f1b6