[qmf] Fix double emiting of messageUpdate/messageAdded signal.

Double emition was introduced by this commit:
https://qt.gitorious.org/qt-labs/messagingframework/commit/9aca2eb83a164d3da4bce635eca58e9f3751ca95
When data or properties are updated in the store instance respective messageUpdate/messageAdded signals
are already emitted.
Yeah, it seems that the origin process is filtered out before we get to this function.

What a maze this code is... I give up, I can't work out if you're right from reading it, I assume your testing proves so :-)
The double notification is in the processes receiving IPC notifications, right?  Do we have any unit tests that can be adapted to verify this is now correct?