inetd: convert remaining bzero(3) to memset(3), NFC

This change is purely in the name of noise reduction from static analyzers
that want to complain that bzero(3) is obsolete in favor of memset(3).

With this, clang-analyze at least is now noise free. WARNS= 6 also appears
to have been OK for some time now, so drop the current setting and opt for
the default.