Stop hang detect timer when flags are set to 0
Stop hang detect timer when flags are set to 0

Previously, setting flags=0 would disable any future timers from being
started, but not stop any timer currently in progress.  With this
change, it does.

BUG=chromium:298983
BRANCH=rambi,nyan
TEST=manual
  on ap, ectool hangdetect 1 60000 0
  on ec, hangdet -> status=inactive
  press power button
  on ec, hangdet -> status=active for event
  on ap, ectool hangdetect 0 0 0
  on ec, hangdet -> status=inactive

Change-Id: Icf8c6e0e95ae3780d250f9f01ec6a4dda6c56176
Signed-off-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/184950
Reviewed-by: Daniel Erat <69d56254d3d393520d06e9838c23c147a5fee7d9@chromium.org>
Reviewed-by: Alec Berg <1a4429eeda29095a12e19a73405f80f5b7f37a63@chromium.org>

coreboot/chrome-ec,alterapraxisptyltd/chromium-ec,longsleep/ec,eatbyte/chromium-ec,akappy7/ChromeOS_EC_LED_Diagnostics,mtk09422/chromiumos-platform-ec,md5555/ec,eatbyte/chromium-ec,fourier49/BZ_DEV_EC,thehobn/ec,gelraen/cros-ec,akappy7/ChromeOS_EC_LED_Diagnostics,md5555/ec,longsleep/ec,alterapraxisptyltd/chromium-ec,coreboot/chrome-ec,md5555/ec,fourier49/BIZ_EC,coreboot/chrome-ec,fourier49/BIZ_EC,thehobn/ec,coreboot/chrome-ec,thehobn/ec,alterapraxisptyltd/chromium-ec,longsleep/ec,mtk09422/chromiumos-platform-ec,thehobn/ec,mtk09422/chromiumos-platform-ec,gelraen/cros-ec,coreboot/chrome-ec,longsleep/ec,coreboot/chrome-ec,gelraen/cros-ec,alterapraxisptyltd/chromium-ec,mtk09422/chromiumos-platform-ec,fourier49/BZ_DEV_EC,fourier49/BIZ_EC,akappy7/ChromeOS_EC_LED_Diagnostics,eatbyte/chromium-ec,md5555/ec,fourier49/BIZ_EC,gelraen/cros-ec,akappy7/ChromeOS_EC_LED_Diagnostics,fourier49/BZ_DEV_EC,akappy7/ChromeOS_EC_LED_Diagnostics,fourier49/BZ_DEV_EC,eatbyte/chromium-ec