nfsd: Add a KASSERT in nfsvno_open

Commit ded5f2954e 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().
This only happens when nfsvno_namei() is done with CREATE.

This patch adds a KASSERT() to check for that.

PR:	268971

sys/fs/nfsserver/nfs_nfsdport.c

@@ -1926,6 +1926,8 @@ nfsvno_open(struct nfsrv_descript *nd, struct nameidata *ndp,
 			}
 		}
 	} else if (done_namei) {
+		KASSERT(create == NFSV4OPEN_CREATE,
+		    ("nfsvno_open: not create"));
 		/*
 		 * done_namei is set when nfsvno_namei() has completed
 		 * successfully, but a subsequent error was set in