ors-image-backports: set MTU to 1500 on lo for ORS
When IPv6 between gNB and MME on different ORS, TCP throughput between phones with MTU 1500 and ORS is very bad. Setting MTU to 1500 on lo (where the eNB / MME GTP addresses are) fixes the issue.
Unfortunately this also reduces MTU for all local packets which is not great, but the alternative would be to move partition addresses to a different interface.
/cc @tomo