net: use member clientInterface rather than global uiInterface in CConman

Summary:
And rename it m_client_interface to match BanMan

This is a backport of core#22732

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D13349