(#14615) Exclude helperscripts in gentoo service provider

The directory /etc/init.d does not only store normal initscripts but
also a few helper scripts (like functions.sh). The former behaviour was
to treat them as regular initscripts which can lead to dangerous results
especially when running puppet resource service. This command will
issue /etc/init.d/<script> status on every script inside
/etc/init.d. Because the helperscripts don't care about arguments,
this will cause the system to reboot when /etc/init.d/reboot.sh status is
executed.

Exclude helperscripts when searching inside /etc/init.d.