bisect-kit: fix psutil api usage

psutil.Process.get_children() has been deprecated since 2.0.0 and
removed since 3.0.0. Use children() instead.

BUG=chromium:776314
TEST=unittest pass with psutil 3+

Change-Id: Ia3792897b5f892ee1a35887f6ffe91ca3e9ef110
Reviewed-on: https://chromium-review.googlesource.com/792890
Commit-Ready: Kuang-che Wu <kcwu@chromium.org>
Tested-by: Kuang-che Wu <kcwu@chromium.org>
Reviewed-by: Owen Lin <owenlin@chromium.org>
1 file changed