Changes to pixel tracking at HLT

This MR makes three changes:

• sets minClusters in minBiasPixel configuration, which is used to set minHits in InDetTrigAmbiTrackSelectionTool,
• sets minSiClusters in TrigAmbiguityScoringTool for minBiasPixel,
• moves pixsptrk chains from HI Dev to Physics menu.

With these changes, the HLT_mb_pixsptrk_* chains are producing counts. Both HLT containers (HLT_PixelTrackCount and HLT_IDTrack_MinBiasPixel) are present in RDO_TRIG, but are not propagated to AOD. Workdir on lxplus: ~kciesla/public/pixsptrk.

CC: @tbold @sutt @bkerridg