util: added a reverse insert (sorted) routine to TAILQ

This changes the way in which equal objects are handled. Previously they'd
be added to the HEAD and with this they add to the TAIL, which is what I
need in network scanning code.
mpegts network_scan: fix queue ordering issue

This was causing entries just complete (idle scan) to get re-added to the head!
Which ultimately resulted in only N entries ever getting serviced (where N is
the number of available tuners)