Handle invalid libpq sockets in more places

Peter Eisentraut <peter_e@gmx.net>

Commit: a40814d7aacbda9266c703cc011d3506668899de
Author: Peter Eisentraut <peter_e@gmx.net>
Date: 2016-03-09T02:10:33Z
Releases: 9.6.0
Handle invalid libpq sockets in more places

Also, make error messages consistent.

From: Michael Paquier <michael.paquier@gmail.com>

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