Fix IPv6 connectivity
Summary:
IPv6 is supported by LibVNCServer but for compatibility reasons its
socket is backed by another file descriptor.
This commit adds tracking IPv6 listen socket in the same way we now
track IPv4 one.
Test Plan: Tested by connecting through ::1 and fe80:: addresses
Reviewers: Plasma, KDE Applications, alexeymin
Reviewed By: alexeymin
Subscribers: ltoscano, alexeymin, apol, aacid
Differential Revision: https://phabricator.kde.org/D13209