Add missing const to CAddrMan::Check_()

Summary:

Also: Always compile the function signature to avoid similar issues in the future.

Partial backport of core#20233:
https://github.com/bitcoin/bitcoin/pull/20233/commits/ee458d84fc187d69f002ebead6fccc4f4f9c0744

Test Plan:
With DEBUG_ADDRMAN:

ninja all check

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D12270