Revert "mpegts: Make sure we don't return uninitialized packets"

This change broke data streams, particularly DSMCC packets were
rejected which in turn broke MHEG Interactive Services e.g. 'Red
Button' services

This reverts commit 2ea63fc01cec3a7a87c1ec2279dbb08ff8f21445.
Add a setting to control MHEG interaction channel, patch by Lawrence Rust

This also disables the interaction channel (and iplayer) by default as
it appears that this is currently broken, possibly by an upstream
change at the BBC.
Tidy comment