[sol005robot] SOL005/VNFPackageManagement-API/environment: Too many variable files

The variables required for the suite tests are spread over too many files, making the testing process very tedious. Finding the appropriate variable requires going through each file.

On top of this, some variables are (re)defined multiple times. For example, erroneousVnfPkgId is defined in vnfPackageContent.txt, vnfdInIndividualVnfPackage.txt and vnfPackageArtifacts.txt.