busybox

ftpd: make DIR parameter work for non-root too: chdir to it instead of chroot

Unfortunately, chroot() works only for root user, because of attacks
on setuid binaries (make DIR/lib/ld-linux.so a shell, hardlink to
a setuid binary, chroot to DIR, execute it and get root shell).

function                                             old     new   delta
ftpd_main                                           2160    2180     +20

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>