package: don't hide webservers when !BR2_PACKAGE_BUSYBOX_SHOW_OTHERS

The busybox web server isn't providing the same binary name / cmdline
arguments as the "big" webservers, so they aren't equivalent.

As discussed on the dev day, don't hide them when _SHOW_OTHERS isn't
enabled.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>