fix RNAseq testdata

There were two parameters missing from essential.vars.groovy, which are required for cutadapt.

Also, the pipeline was using star v2.7.10a by default, for which there is currently no index available at /fsimb/common/genomes/saccharomyces_cerevisiae/ensembl/R64/canonical/index/star/

The alternative would be to create an index, but from what I understood from talking to @skarunan, star v2.7.3a should remain the preferred version for now