Fix meatspace-proxies handling of previously seen messages,  don't utilize meatspace backscroll to avoid replaying meatspace versions of seatcamp messages.
Fix meatspace-proxies handling of previously seen messages,  don't utilize meatspace backscroll to avoid replaying meatspace versions of seatcamp messages.

brycebaril/seatcamp,teltploek/bacid,teltploek/bacid,tec27/seatcamp,brycebaril/seatcamp,tec27/seatcamp