manually search for vertex from track in PhotonVertexSelectionTool
This MR fix a compilation problem, see ATLASG-1547
This class is affected by the change in #8bcdfff4 where the links from track to their corresponding vertices are removed. Here the search is done manually (as in many other clients changed in the cited commit above).
I am not using ReadHandler
to get the vertex container since they are not used in this class.
Closes ATLASG-1547