mpegts: fix broken input handling for inputs with >1 active services..

This affects IPTV where there is only 1 input, if 2 services have the same PIDs
then both services were receiving each others packets and causing a mess!

I think later on I should really remove the transport list from the input and
have it on the mux? I think I did it this way to keep some things simpler, but
it's caused confusion here.

This should fix #1875.