Reorder execution stack of Flow Element linkers to Tau and validation plots drawing from them

Hi (cc @cdelitzs @mhodgkin @mswiatlo @lmiller)

This merge request re-orders the production of validation plots to be after all algorithms which are used as inputs (Basically, the Flow Element linkers to Taus is much later in the execution stack than the others).

The simplest means to do this was to explicitly require that the validation plots are produced directly after the last linker algorithm (in this case the tau links). This MR produces desired tau linker plots without a re-run over AOD.

This is a python only configuration change, so if this could please be expedited, that would be great!

Thanks

Matt A.