Parameterize internal image names for node/mem/io hog scenarios to support disconnected environments

[avyas26]

In the node/mem/io hog scenarios, below two images are called internally from the parent image i.e.,

• quay.io/arcalot/arcaflow-plugin-kubeconfig:0.2.0
• quay.io/arcalot/arcaflow-plugin-stressng:0.3.1

In disconnected environments, these images will be pulled from a connected host and mirrored on to a local registry. The image names will have to be changed in order to pull it from the local mirror, instead of Quay.