[avalanche] Cleanup the proof voting test

Summary:

• Remove dangling log
• Remove duplicated test case
• Remove duplicated peer
• Remove the wait_for_disconnect and whitelist the locahost. This leads to a minor duration gain which will turn huge in the next diff.

Test Plan:

./test/functional/test_runner.py abc_p2p_avalanche_proof_voting

Reviewers: #bitcoin_abc, sdulfari

Reviewed By: #bitcoin_abc, sdulfari

Differential Revision: https://reviews.bitcoinabc.org/D12176