nfs4: Fix kmemleak when allocate slot failed

nfs4: Fix kmemleak when allocate slot failed

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 v5.10.154 by commit 45aea4fbf61e205649c29200726b9f45c1718a67, it was introduced in version v3.12 by commit abf79bb341bf52f75f295b850abdf5f78f584311. For more details please see the references link.