amt: properly arm/disarm timer, remove unnecessary code
Addresses #25228 (closed)
- Leave disarm timer to avoid data race, but properly initialize the timer once AMT packets are confirmed received
- Multiple testing on this with stream left for an hour, IGMP reports are sent at correct interval
- Remove unneeded code, saw the TODO and went ahead and tested without it
- seems to have been remnant of an older gateway implementation not done in VLC