net: avoid unnecessary GetBindAddress() call

Summary:
Our local (bind) address is already saved in CNode::addrBind and there
is no need to re-retrieve it again with GetBindAddress().

Also, for I2P connections CNode::addrBind would contain our I2P
address, but GetBindAddress() would return something like
127.0.0.1:RANDOM_PORT.

This is a backport of core#20685 [7/20]
https://github.com/bitcoin/bitcoin/pull/20685/commits/f6c267db3be2d7077fd2bdbd34860eba838dea99

Depends on D11015

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D11016