devserver: add ongoing au process number check in check_health.
This CL mainly does:
1. Add checking the number of current background au processes in
check_healthy devserver call.
2. Force kill_au_proc to kill the au process if the process's pid is
passed.
BUG=chromium:696606
TEST=Run local devserver and call check_health & kill_au_proc.
Change-Id: I4fe44407b85659bd3aab309ac8efe11b0b457f68
Reviewed-on: https://chromium-review.googlesource.com/447821
Reviewed-by: Aviv Keshet <akeshet@chromium.org>
Commit-Queue: Xixuan Wu <xixuan@chromium.org>
Tested-by: Xixuan Wu <xixuan@chromium.org>
2 files changed
