Fix nested-overlayfs POSIX ACL tests (recursive lockdep issue)

### Description

The overlayfs locks need to be adjusted to properly handle the lock recursion that happens with overlayfs-on-overlayfs.

This will allow two tests, SetACLThroughStackedOverlay and GetACLThroughStackedOverlay, to be re-enabled.

Note that this issue is solely an issue with lockdep enabled (our syscall tests + syzkaller). It is not reachable in a production gVisor build.
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