commons: update RequestExecutionTimeGauges to accept units

Update nfs door/mover to use correct units, e.g. 'ns'.
Fix gauge's min value and format.

Acked-by: Albert Rossi
Target: master
Require-book: no
Require-notes: no
commons: remove period based gauges

The RequestExecutionTimeGauge has a possibility to have
period based average. This functionality can be replaced
by having two gauges - one to full time period and
second for a desired time period.

Acked-by: Albert Rossi
Target: master
Require-book: no
Require-notes: no