docker: podman-friendly image locations

Adds fully qualified canonical locations of container images, making the
container technology setup podman-friendly.

Closes reanahub/reana#729.

Dockerfile

@@ -4,7 +4,7 @@
 # REANA is free software; you can redistribute it and/or modify it
 # under the terms of the MIT License; see LICENSE file for more details.
 
-FROM rabbitmq:3.8-management
+FROM docker.io/library/rabbitmq:3.8-management
 
 ENV RABBITMQ_NODENAME=rabbit@localhost
 ARG DEBUG=0

run-tests.sh

@@ -1,7 +1,7 @@
 #!/bin/bash
 #
 # This file is part of REANA.
-# Copyright (C) 2017, 2018, 2020, 2021 CERN.
+# Copyright (C) 2017, 2018, 2020, 2021, 2023 CERN.
 #
 # REANA is free software; you can redistribute it and/or modify it
 # under the terms of the MIT License; see LICENSE file for more details.
@@ -41,7 +41,7 @@ check_pytest () {
 }
 
 check_dockerfile () {
-    docker run -i --rm hadolint/hadolint:v1.18.2 < Dockerfile
+    docker run -i --rm docker.io/hadolint/hadolint:v1.18.2 < Dockerfile
 }
 
 check_docker_build () {