Revert "proc: fix races against execve() of /proc/PID/fd**"

Revert "proc: fix races against execve() of /proc/PID/fd**"

This reverts commit 5870b51f8bc72e12260679b2a06e9e764231c124.

It escalates of some of the google-chrome SELinux problems with ptrace
("Check failed: pid_ > 0.  Did not find zygote process"), and Andrew
says that it is also causing mystery lockdep reports.

Reported-by: Alex Villacís Lasso <a_villacis@palosanto.com>
Requested-by: James Morris <jmorris@namei.org>
Requested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>