Recategorize seeder connections as not manual

Summary:
After the seeder is started, there is no user input. As such, the
connections the seeder makes should not be considered manual.

Test Plan:

ninja
./bitcoin-seeder -host=localhost -ns=blah.bitframe.org -port=8888 -mbox=info@bitframe.org --testnet --wipeban --wipeignore

There should be no behavioral changes.

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, deadalnix

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D6176