Fix jiffy hz to milliseconds calculation in CarServiceHelperService.

- Update proc stat parsing regex to capture values with named groups.

Test: m -j google-tradefed-all; tools/tradefederation/core/tradefed.sh \
run google/test/car/health/watchdog/car-watchdog-reliability.xml
Bug: 213939034

Change-Id: I277912fa8937c91e544583ef5c7b37d8b48323d9