Revert "futex: Always cleanup owner tid in unlock_pi"

This reverts commit 75e06324ec6059fbb4d1cd78a6dbfd7b6e0d7f5b.
Revert "futex: Validate atomic acquisition in futex_lock_pi_atomic()"

This reverts commit ddddfcf29bfb9cd793caa1cb23e3f10e3e883613.
Revert "futex: Prevent attaching to kernel threads"

This reverts commit 12befa1c326f2355d51b4b88de8bf28dad948e96.
Revert "futex-prevent-requeue-pi-on-same-futex.patch futex: Forbid uaddr == uaddr2 in futex_requeue(..., requeue_pi=1)"

This reverts commit f56484ac7cc852a55c4f710face3c667320b55f7.