docker: podman-friendly image locations

[tiborsimko]

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

Closes reanahub/reana#729.

[codecov-commenter]

Codecov Report

Merging #604 (607e26e) into master (b848c11) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #604   +/-   ##
=======================================
  Coverage   59.30%   59.30%           
=======================================
  Files          32       32           
  Lines        3229     3229           
=======================================
  Hits         1915     1915           
  Misses       1314     1314           

[mdonadoni]

Should we change also the docker image in run-tests.sh? This applies also to the other repositories

reana-server/run-tests.sh

Line 46 in c459270

docker run --rm --name postgres__reana-server -p 5432:5432 -e POSTGRES_PASSWORD=mysecretpassword -d postgres:12.13

reana-server/run-tests.sh

Lines 92 to 98 in c459270

	check_dockerfile () {
	docker run -i --rm hadolint/hadolint:v1.18.2 < Dockerfile
	}
	check_docker_build () {
	docker build -t reanahub/reana-server .
	}