fixed array combination in tests

it should be done via concat not +

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
bugfix: prevent duplications in repository list

solves #29

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
bugfix: prevent duplication of nodes when fetching multiple times

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
test for package duplication with multiple fetches

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
Merge pull request #30 from TelekomCloud/bugfix/duplications

Thanks.