Bug#914397: nftables: after Stretch->Buster upgrade, named set needs "auto-merge"

[Gert]

Whoops, the "System Information" is not from the affected system, but 
from the system I used to write the report. So ignore that.

System Information from the affected system:
linux-image-4.18.0-2-amd64 4.18.10-2+b1
nftables 0.9.0-1
libnftables0 0.9.0-1
libnftnl7 1.1.1-1
libxtables12 1.8.2-2
libgmp10 2:6.1.2+dfsg-3
libmnl0 1.0.4-2
libreadline7 7.0-5