FIX: Fix failing RegisterUsingSlidingGeometries test.

     Test 13 was failing because the baseline image on MIDAS
     does not seem to be a valid motion field.

     We decided to correct the baseline in that case.
Merge pull request #82 from rkwitt/Fix-RegisterUsingSlidingGeometriesFailingTest

FIX: Fix failing RegisterUsingSlidingGeometries test