adjust hiding client input to satisfy toybox

adjust hiding client input to satisfy toybox

when done reading from the client, we defensively close stdin, to
prevent potential bugs being exploitable to malicious input

toybox opens /dev/null if stdin does not exist, which crashes in a
chrooted evironment. piping in an empty string more or less
accomplishes the same thing as closing stdin would

i really do not know why toybox found this necessary.