inetd: track all child pids, regardless of maxchild spec

Currently, child pids are only tracked if maxchildren is specified. As a
consequence, without a maxchild limit we do not get a notice in syslog on
children aborting abnormally. This turns out to be a great debugging aide at
times.

Children are now tracked in a LIST; the management interface is decidedly
less painful when there's no upper bound on the number of entries we may
have at the cost of one small allocation per connection.

PR: 70335