docker: align spinner to center (#9814)
docker: align spinner to center (#9814)

fixes #6106
mvollmer/cockpit,cockpit-project/cockpit,andreasn/cockpit,mvollmer/cockpit,cockpit-project/cockpit,deryni/cockpit,martinpitt/cockpit,martinpitt/cockpit,garrett/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,cockpituous/cockpit,garrett/cockpit,cockpituous/cockpit,martinpitt/cockpit,deryni/cockpit,garrett/cockpit,andreasn/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,andreasn/cockpit,martinpitt/cockpit,cockpit-project/cockpit,garrett/cockpit,cockpituous/cockpit,deryni/cockpit,deryni/cockpit,cockpituous/cockpit,cockpituous/cockpit,garrett/cockpit,andreasn/cockpit,mvollmer/cockpit,andreasn/cockpit,andreasn/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,deryni/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,cockpituous/cockpit,deryni/cockpit,deryni/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,andreasn/cockpit