nfsd: Fix handling of the error case for nfsvno_open some more

Commit ded5f2954e1a defined done_namei to indicate that
nd_repstat was set after a successful nfsvno_namei(),
so that a cleanup needs to be done in nfsvno_open().
However, it missed the case where a call to
nfsrv_opencheck() in nfsvno_open() sets nd_repstat non-zero.

This would cause panics due to a dangling locked vnode
when nfsrv_opencheck() set nd_repstat, such as during grace
just after a server boot.

This patch fixes the problem.

PR: 268971