Fix "QIODevice::read" warnings.
Summary:
Calling readAll() after close() leads to this warning because QIODevice checks
the open status before reading, and warns (and returns -1) if closed.
Let's just create a different socket in doReconnect to make sure we have
no interference from the just closed one.
Test Plan: ctest --verbose -R sqlite-tagtest no longer has all these warnings.
Reviewers: dvratil, sengels
Subscribers: kde-pim
Tags: KDE PIM
Differential Revision: https://phabricator.kde.org/D18558