Wait for the disconnected peers to be accounted in the getavalancheinfo test

Summary: Upon disconnect the node enqueues a finalization event that is used to update the avalanche peer manager state. Let's make sure we wait for this even to be accounted.

Test Plan:

./test/functional/test_runner.py abc_rpc_getavalancheinfo

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D17342