Merge #12326: net: initialize socket to avoid closing random fd's

Summary:
96dbd38 net: initialize socket to avoid closing random fd's (Cory Fields)

Pull request description:

An excellent spot by @david60.

Even if it isn't causing the fd issue we're looking for, this should be fixed.

Tree-SHA512: 062a8f2cdd39d895213e1263dbd7b8391473ddaea2f93c82c211a9bb6ea6744d48a6c84c8ff804b16b865d14145492635c500a9fd138d0988fee5e4f719ebb91

Backport of Core PR 12326
https://github.com/bitcoin/bitcoin/pull/12326/files
Reviewer note: setting hSocket = INVALID_SOCKET was already backported.

Test Plan: make check

Reviewers: deadalnix, Fabien, #bitcoin_abc

Reviewed By: Fabien, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D2959