Use FILES+= idiom instead of _inetd when referencing inetd rc.d script

This was a discrepancy between ^/projects/building-blocks and ^/head that I
didn't resolve before committing the change to ^/head

Pointyhat to: me
Reported by: jhb
MFC after: 20 days
X-MFC with: r278249
Sponsored by: EMC / Isilon Storage Division