Re-compute correct timeslot on applyModemConfig

[thebentern]

Per our conversation in contributors room in Discord
Closes #3892

[GUVWAF]

Looks good, but we might want to decrease CWmax then also. Currently the absolute maximum delay on LongFast before rebroadcasting is 2^8 * slotTimeMsec = 10.7 seconds, which will become 19.7 seconds. Maybe we can decrease CWmax to 7 such that we get 9.86 seconds?

[thebentern]

Looks good, but we might want to decrease CWmax then also. Currently the absolute maximum delay on LongFast before rebroadcasting is 2^8 * slotTimeMsec = 10.7 seconds, which will become 19.7 seconds. Maybe we can decrease CWmax to 7 such that we get 9.86 seconds?

See this is why I added you :-)