store maxSendQBytes in a uint32 to avoid alignment problems
The sync.atomic documentation says:
"On both ARM and x86-32, it is the caller's responsibility to arrange
for 64-bit alignment of 64-bit words accessed atomically."
This moves channel registration to an eventual consistency model,
where the in-memory datastructures (Channel and ChannelManager)
are the exclusive source of truth, and updates to them get persisted
asynchronously to the DB.