Count each processor package once, never read a sleeping card, and give no reading for a reset counter (hq ADR 0255)

Intel shows some packages twice (MSR and MMIO), an AMD card's sensors wake it, and a
counter reset after resume read as thousands of watts. The loop's cadence and the bar
script's staleness are now tested, and the sampler running on every machine is said.

modules/power/files/bin/power-draw

@@ -4,7 +4,7 @@
 # Prints the line the module's sampler (`power draw`, as root) publishes every five seconds, which says
 # what it measured: "machine" on battery, "CPU" or "CPU+GPU" otherwise. A line older than thirty
 # seconds is a sampler that stopped, and is not shown as if it were now.
-f=/run/mesh-power/draw
+f="${MESH_POWER_DRAW:-/run/mesh-power/draw}"
 if [ -r "$f" ] && [ $(( $(date +%s) - $(stat -c %Y "$f") )) -le 30 ]; then
 	head -n 1 "$f"
 else