bots: Fix EPEL install on rhel-7* images
bots: Fix EPEL install on rhel-7* images

`yum install -y epel-release` works on CentOS 7, but not on RHEL 7. Move
the wget-based enabling of EPEL to an earlier place so that it works
everywhere.

Fixes #8253

Closes #8283

mareklibra/cockpit,SotolitoLabs/cockpit,moraleslazaro/cockpit,mareklibra/cockpit,garrett/cockpit,Scribery/cockpit,stefwalter/cockpit,moraleslazaro/cockpit,SotolitoLabs/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,Scribery/cockpit,Scribery/cockpit,cockpit-project/cockpit,mareklibra/cockpit,mareklibra/cockpit,petervo/cockpit,martinpitt/cockpit,garrett/cockpit,petervo/cockpit,martinpitt/cockpit,petervo/cockpit,petervo/cockpit,stefwalter/cockpit,cockpituous/cockpit,petervo/cockpit,andreasn/cockpit,deryni/cockpit,andreasn/cockpit,moraleslazaro/cockpit,garrett/cockpit,martinpitt/cockpit,andreasn/cockpit,SotolitoLabs/cockpit,mareklibra/cockpit,cockpit-project/cockpit,cockpituous/cockpit,petervo/cockpit,andreasn/cockpit,SotolitoLabs/cockpit,mvollmer/cockpit,stefwalter/cockpit,andreasn/cockpit,deryni/cockpit,SotolitoLabs/cockpit,garrett/cockpit,deryni/cockpit,SotolitoLabs/cockpit,Scribery/cockpit,moraleslazaro/cockpit,cockpituous/cockpit,Scribery/cockpit,stefwalter/cockpit,deryni/cockpit,deryni/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,stefwalter/cockpit,mvollmer/cockpit,stefwalter/cockpit,andreasn/cockpit,cockpit-project/cockpit,martinpitt/cockpit,mvollmer/cockpit,cockpituous/cockpit,deryni/cockpit,stefwalter/cockpit,martinpitt/cockpit,petervo/cockpit,garrett/cockpit,mareklibra/cockpit,moraleslazaro/cockpit,andreasn/cockpit,cockpituous/cockpit,deryni/cockpit,cockpituous/cockpit,Scribery/cockpit,Scribery/cockpit,mareklibra/cockpit,SotolitoLabs/cockpit,moraleslazaro/cockpit,mvollmer/cockpit