futex: Always cleanup owner tid in unlock_pi

futex: Always cleanup owner tid in unlock_pi

If the owner died bit is set at futex_unlock_pi, we currently do not
cleanup the user space futex.  So the owner TID of the current owner
(the unlocker) persists.  That's observable inconsistant state,
especially when the ownership of the pi state got transferred.

Clean it up unconditionally.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: Will Drewry <wad@chromium.org>
Cc: Darren Hart <dvhart@linux.intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 13fbca4c6ecd96ec1a1cfa2e4f2ce191fe928a5e)
[wt: adjusted context - cmpxchg_futex_value_locked() takes 3 args]
Signed-off-by: Willy Tarreau <w@1wt.eu>