Move task of cleaning up socket file to FdReceiver

Summary:
The class SocketAddress is meant only for creating a proper socket address structure.
It should not be cleaning up socket files. FdReceiver is better suited for this job.

Reviewers: Frameworks, ossi, dfaure

Reviewed By: ossi, dfaure

Subscribers: kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D10410