Revert "oom_kill.c: futex: delay the OOM reaper to allow time for proper futex cleanup"

This reverts commit 0441d3e9.  It breaks
the abi and is not needed for Android devices.

Bug: 161946584
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I0d9f161b4250bb6ec960e2a5ee2f425f6f8dbf4e