ExecutiveTest.serial_test_kill_process is still unreliable on windows

Just giving up on this test, it tried to work around windows oddity
but we clearly still don't understand what windows is doing
so just skipping the test.

Review URL: https://codereview.chromium.org/305613003

git-svn-id: svn://svn.chromium.org/blink/trunk@174998 bbb929c8-8fbe-4397-9dbb-9b2b20218538