Bug fix: GRID link extraction

Bug description

Grid link extraction was broken as described in #79 (closed). This happened when a chain of multiple links was used that had different levels wrt the base directory:

[sargyrop@lxplus704]~/mcjoboptions/950xxx/950031% readlink mc_13TeV.Sh_228_ttbar_AllHadronic_EnhMaxHTavrgTopPT.GRID.tar.gz
../../700xxx/700050/mc_13TeV.Sh_228_ttbar_AllHadronic_EnhMaxHTavrgTopPT.GRID.tar.gz
[sargyrop@lxplus704]~/mcjoboptions/950xxx/950031% readlink ../../700xxx/700050/mc_13TeV.Sh_228_ttbar_AllHadronic_EnhMaxHTavrgTopPT.GRID.tar.gz
../700047/mc_13TeV.Sh_228_ttbar_AllHadronic_EnhMaxHTavrgTopPT.GRID.tar.gz

instead of ../../700047/mc_13TeV.Sh_228_ttbar_AllHadronic_EnhMaxHTavrgTopPT.GRID.tar.gz

Solution

The scripts now cd to the directory where the links are pointing after every link extraction.

Tests

Test passed here: https://gitlab.cern.ch/atlas-physics/pmg/mcjoboptions/pipelines/1434723

Closes #79 (closed)