Avoid the p2p delays on some functional tests

Summary: I frequently ran these tests recencently and noticed that they could benefit from a localhost noban whitelist option to speed up the test (about x10 on rpc_packages) or get a more consistent timing.

Test Plan:

ninja check-functional

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D16497