Test regression link storage new file

* Adds regression test for link storage to make sure a new file
  in Blueprint A that should overwrite a file in Blueprint B
  is taken into consideration.

Signed-off-by: Javier Martin Montull <javier.martin.montull@cern.ch>
Fixes storage link new file regression

Signed-off-by: Javier Martin Montull <javier.martin.montull@cern.ch>