Prevent ProcessTest::ResetPidByFile from killing any innocent process.

BUG=chromium:308196
TEST=Tested the following:
1. FEATURES=test emerge-$BOARD platform2
2. Run libchromeos-180609_unittests and libchromeos-242728_unittests
   under strace and verify that the ProcessTest::ResetPidByFile unit
   test doesn't send SIGKILL to a random process with pid 456.

(cherry picked from commit 3d14cae18da2bf58bd111533b8ce95d956b4735c)

Change-Id: Ia95bba747ffee063f63a1813fbbc7b1140914848
Reviewed-on: https://chromium-review.googlesource.com/188906
Reviewed-by: Ben Chan <benchan@chromium.org>
Commit-Queue: Ben Chan <benchan@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
2 files changed