Increase maxconnections limit when using poll.
Summary:
Partial backport of Core PR14336
https://github.com/bitcoin/bitcoin/pull/14336/commits/4927bf2f257ac53569978980eaf1f61c2c6b04cc
Depends on D6470
Test Plan:
ninja ninja check-all src/bitcoind --debug=net
Verify normal node behavior.
Reviewers: O1 Bitcoin ABC, #bitcoin_abc, majcosta
Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, majcosta
Subscribers: majcosta
Differential Revision: https://reviews.bitcoinabc.org/D6471