[chronik] Make chronik_serve bind once to the same ip

Summary: The datadir's default config file from the test framework always adds a binding to 127.0.0.1 which is not what the test is expecting.

Test Plan:

./test/functional/test_runner.py chronik_serve

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Subscribers: PiRK

Differential Revision: https://reviews.bitcoinabc.org/D15730