bots: Declare rhel-7-7 image
bots: Declare rhel-7-7 image

Closes #11375
martinpitt/cockpit,cockpit-project/cockpit,deryni/cockpit,cockpit-project/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,deryni/cockpit,garrett/cockpit,deryni/cockpit,garrett/cockpit,moraleslazaro/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,martinpitt/cockpit,deryni/cockpit,moraleslazaro/cockpit,garrett/cockpit,cockpituous/cockpit,garrett/cockpit,garrett/cockpit,moraleslazaro/cockpit,martinpitt/cockpit,cockpituous/cockpit,mvollmer/cockpit,cockpituous/cockpit,cockpituous/cockpit,moraleslazaro/cockpit,deryni/cockpit,deryni/cockpit,mvollmer/cockpit,cockpituous/cockpit,mvollmer/cockpit,cockpit-project/cockpit,deryni/cockpit,martinpitt/cockpit,cockpit-project/cockpit,mvollmer/cockpit,cockpituous/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit