PersistentImageToVectorData process the input twice when only one stream is used
Mantis Issue 310, reported by jmalik, assigned to jmalik, created: 2011-05-23
We end up with a VectorData where each feature is present twice.
This problem may also be present for all the other "Persistent" filters.
1306238689 - julienmfixed in http://hg.orfeo-toolbox.org/OTB/rev/7d3141b2392d