busybox

mount: ignore unknown mount options when remounting NFS mounts

Don't fail on unknown nfs mount options. The kernel automatically
adds a few mount options that we don't currently handle, like:

	sec=null|sys|krb5..
	mountaddr=<ip>
	mountproto=tcp|udp
	local_lock=none|all|flock|posix

Which causes a simple mount -o remount,rw <mountpoint> to fail.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>