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 v5.4.224 by commit 925cb538bd5851154602818dc80bf4b4d924c127, it was introduced in version v3.12 by commit abf79bb341bf52f75f295b850abdf5f78f584311. For more details please see the references link.