Tracks duplicated in radsxogen when creating both single and dual satellite xovers

[remkos]

This issue was found during the analysis of issue #127.

When generating both single and dual satellite crossovers with radsxogen, the track count and the list of tracks is duplicated, one set created when generating single satellite crossovers, one when generating dual-satellite crossovers.

The duplicate tracks need to be condensed to single tracks.

For example, radsxogen --ymd=20170510,20170520 -Sj2 -Sj3 creates 922 instead of 461 tracks.

[remkos]

Closed by commit 167d7e3