Fix GapSeq Tests

[pbelmann]

Database files provided by gapseq can no longer be downloaded (see jotech/gapseq#195) and leads to ci runs that never finish. With PR #339 gapseq is replaced with carveme. However, carveme needs a cplex binary which must be part of the container and makes it difficult for a user to run the toolkit. Carveme should be replaced with gapseq as soon as the database files can be downloaded again.