|Thank you so much for helping me with this Ben.|
So yes I do need to be ROOT to set those permissions.
I tried to use docker command, but I don't know exactly where it ties in with Openshift's registry. That image is in fact from RedHat's private repository and while I can use it from within Openshift it doesn't look like I can "access" it otherwise (I don't have a license for it, I know it's bad but I can't afford to make the changes to my code in order to use e.g. wildfly).
Oh well, I'll try to avoid using this modified container in the first place.