Randomize shard list for each CI_DRM_* run
So we don't have to wait for a new
IGT_ run to get the list reshuffled. With this we can
CI_DRM_ we already know with which IGT it will be paired, so we can grab the list and shuffle it there. Another option would be to do this when running shardfeed.
This would help with cibuglog#78 (closed)
PS. IGT containers do not have shard testlist baked into it. When we will move CI execution to them we will have to provide the lists separately and this would prepare us for it.