fs/nfsd: Disable NFSD_LEGACY_CLIENT_TRACKING

Disabling the NFSD legacy client tracking will fix as consequence issues like #1087900.

A targeted solution for fixing #1087900 is currently pending upstream as per https://lore.kernel.org/linux-nfs/032ff3ad487ce63656f95c6cdf3db8543fb0d061.camel@kernel.org/T/#t

NFSD legacy client tracking is deprecated and will eventually be removed.