move code for getting merge_statefiles script

As seen in real pipelines and testing in https://xci32.lab.eng.rdu2.redhat.com/cki-project/cki-pipeline/-/jobs/502061, the RDMA jobs are failing, because merge_statefiles.py script isn't found. It looks like we're in a different directory. Because this is used only at 1 place, an inexpensive fix is to just move getting the file itself, which can't make the situation worse.

Signed-off-by: Jakub Racek jracek@redhat.com