Now that Conn::set_conn is guaranteed to be called at the beginning and
at the end of the connection, we can skip re-setting the elements that
we know will not have changed. This prevents repeated lookups, e.g. to
check that addresses are in the local networks.
During `connection_state_remove`, only the duration, number of
packets, service, and history fields are updated.
local_orig and local_resp are updated when the connection is flipped. A
test was added for that purpose. It uses the already existing
http.zeek-image-post-1080-8000-x.pcap, which was slightly rewritten for
this, so that one side of the connection has IP addresses different from
127.0.0.1.
The existing history-flip test also was updated to have one side being
in a local-net, to check that the flipping of local_orig and local_resp
works correctly at the beginning of a connection.