[avalanche] Reduce abc_p2p_proof_inventory.py test duration

Summary: By whitelisting the peers we can cut the time by ~3 to 5 times. This requires to undo the whitelist for a test that checks for disconnection.

Test Plan:

./test/functional/test_runner.py abc_p2p_proof_inventory

Reviewers: #bitcoin_abc, tyler-smith

Reviewed By: #bitcoin_abc, tyler-smith

Subscribers: tyler-smith

Differential Revision: https://reviews.bitcoinabc.org/D11278