Fix scaling issue with Average rate calculation

The 'average rate' calculation appeared to be off by a factor of 10: the base units in Linux[1] are uWh and uAh.

Resolves: #3722 (closed)

[1] https://www.kernel.org/doc/html/latest/power/power_supply_class.html

Signed-off-by: Phil Wise phil@phil-wise.com