Add a work-around to make it possible again to remount

NFS root r/w.

The real solution would be to bring the whole nmount(2)
framework, including FS drivers and userland tools, into
a consistent state at last; but things should work in the
meantime, too.

Reported by:	kris

sbin/mount_nfs/mount_nfs.c

@@ -516,6 +516,15 @@ main(int argc, char *argv[])
 	/* resolve the mountpoint with realpath(3) */
 	(void)checkpath(name, mntpath);
 
+	/*
+	 * XXX This should go away when this NFS implementation
+	 *     is fully converted to nmount(2) semantics.
+	 */
+	if (mntflags & MNT_RDONLY)
+		build_iovec(&iov, &iovlen, "ro", NULL, 0);
+	else if (mntflags & MNT_UPDATE)
+		build_iovec(&iov, &iovlen, "noro", NULL, 0);
+
 	build_iovec(&iov, &iovlen, "nfs_args", nfsargsp, sizeof(*nfsargsp));
 	build_iovec(&iov, &iovlen, "fstype", fstype, (size_t)-1);
 	build_iovec(&iov, &iovlen, "fspath", mntpath, (size_t)-1);