lsof: add busybox tweaks

Since busybox 1.20+ includes a lsof applet make sure lsof gets built
after busybox so that we get the full-blown version if both are enabled.
Also hide the lsof package unless BUSYBOX_SHOW_OTHERS is true.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>