[avalanche] Don't fallback too quickly to regular outbound when looking for an avalanche one

Summary:
The outbound connection thread is prioritizing the avalanche outbounds, however it falls back to regular outbound if the address has no avalanche service bit set. This diff makes the outbound lookup a bit more perseverant by waiting for 50 retries before falling back. There is no change in behavior under normal conditions.

Ref T1696.

Test Plan:

./test/functional/test_runner.py p2p_add_connections

Reviewers: #bitcoin_abc, tyler-smith

Reviewed By: #bitcoin_abc, tyler-smith

Subscribers: tyler-smith

Maniphest Tasks: T1696

Differential Revision: https://reviews.bitcoinabc.org/D11317