abrt-dbus: send new problem notify signal to socket

Since abrtd no longer reacts to new problem dirs, we need to trigger
"post-create" via socket.

This change continues work to implement feature in ticket #657

Signed-off-by: Jakub Filak <jfilak@redhat.com>
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>