InDetVKalVxInJetTool: Fix non-reproducibity in btagging.

The order of tracks in, eg, SV1_TrackParticleLinks, was not reproducible
from run-to-run.  The issue was that in InDetVKalVxInJetTool::GetVrtSec,
the track list was being sorted by pointer value (by a call
to RemoveDoubleEntries).  Resort the list by pt to make the ordering
reproducible.