Avoid recomputation of holes in TrackSummaryTool

As of !36404 (merged), the TrackSummaryTool no longer ignores tracks with existing track summaries. However, this has introduced a bit of a performance regression where it recomputes hole searches for tracks that already have that infomation attached. This commit adds a constraint to the hole search code such that it only runs if the track does not already have hole search information attached to it. As far as I can tell this solves the performance bug.