Fix flakiness in tests that wait for peer info to update immediately after disconnecting peers

Summary:
When a node disconnects, it's connect status is set to false until it's removed from m_nodes in connman.
During this small interval, it is possible for getpeerinfo to report a disconnected node with "connected" as false.
The easiest way to solve this flakiness is to simply wait until getpeerinfo is updated. Calling wait_until is only
necessary immediately after disconnecting a peer, so we do not need to update every check on getpeerinfo in every test.

Test Plan:

./test/functional/test_runner.py abc_p2p_avalanche_remote_proofs p2p_addrfetch feature_maxuploadtarget

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, bytesofman

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D17373