Bypass connectSignal() for receiving the NameOwnerChanged signal

This is an optimization but is required. Instead of going through the
entire (dis)connectSignal() stack to add/remove matching rules for the
NameOwnerChanged bus signal and call into our serviceOwnerChangedNoLock
slot, create a static hook that will match the signal and simply add/
remove the rules as needed.

The required part is that this avoids a recursion into connectSignal().
The next commit will move this code to the QtDBus manager thread and we
won't be able to call connectSignal() from there (it would create a
deadlock).

Change-Id: Iee8cbc07c4434ce9b560ffff13d074ce90ad02d4
Reviewed-by: Albert Astals Cid <aacid@kde.org>
Reviewed-by: Alex Blasche <alexander.blasche@theqtcompany.com>