fix(nfs): mask rpc-svcgssd on server and ha-server build types

nfs-utils changed ConditionPathExists from !/etc/krb5.keytab to
/etc/krb5.keytab, so on IPA-joined hosts the service now starts instead
of skipping. Exports use standard auth (no sec=krb5) so the nfs/ Kerberos
principal is never provisioned and the service fails.

enable = false masks the unit so nfs-server's Wants= can't pull it in.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

modules/build-types/server.nix

@@ -102,6 +102,12 @@ in
     requires = [ "zfs-mount.service" ];
   };
 
+  # rpc-svcgssd handles Kerberos/GSS-API for NFS. Not needed: exports use
+  # standard auth, not sec=krb5. On IPA-joined hosts the keytab exists (host/
+  # principal only) but has no nfs/ principal, causing spurious failure.
+  # Mask it so nfs-server's Wants= can't pull it in.
+  systemd.services.rpc-svcgssd.enable = false;
+
   services.nfs.server = {
     enable = true;
     exports = mkNfsExports vars.storageRoot;