Revert "ovl: relax permission checking on underlying layers"

Revert "ovl: relax permission checking on underlying layers"

This reverts commit 6b1b20e6008ecacb2b4beb3f053bc7a894d6434f.

The commit broke some selinux-testsuite cases, and it looks like there's no
straightforward fix keeping the direction of this patch, so revert for now.

The original patch was trying to fix the consistency of permission checks, and
not an observed bug.  So reverting should be safe.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>