NFSv4/pnfs: Fix a use-after-free bug in open

NFSv4/pnfs: Fix a use-after-free bug in open

This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven.
This ID is fixed in Linux Kernel version v4.19.256 by commit 0fffb46ff3d5ed4668aca96441ec7a25b793bd6f, it was introduced in version v4.19.247 by commit 6b3fc1496e7227cd6a39a80bbfb7588ef7c7a010. For more details please see the references link.