Fix various bugs in the seeder.

Summary:

• fix fubared logs format
• Ensure that the main logger dump on the console just like the rest of the seeder does.
• Ensure connections to new nodes are etablished properly.

Test Plan: Run the seeder manually, ensure it starts crawling the network and that the log look much better.

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien, teamcity

Differential Revision: https://reviews.bitcoinabc.org/D2113