bots: Run rhel-7-6-distropkg tests on master commits
bots: Run rhel-7-6-distropkg tests on master commits

Instead of rhel-7-6. This is more appropriate from now on, as we won't
rebase Cockpit in RHEL 7.6 Base any more.

Closes #9998
martinpitt/cockpit,martinpitt/cockpit,mvollmer/cockpit,garrett/cockpit,cockpituous/cockpit,cockpit-project/cockpit,garrett/cockpit,deryni/cockpit,deryni/cockpit,cockpit-project/cockpit,mvollmer/cockpit,andreasn/cockpit,garrett/cockpit,moraleslazaro/cockpit,garrett/cockpit,andreasn/cockpit,moraleslazaro/cockpit,martinpitt/cockpit,martinpitt/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,andreasn/cockpit,mvollmer/cockpit,deryni/cockpit,andreasn/cockpit,martinpitt/cockpit,andreasn/cockpit,cockpituous/cockpit,deryni/cockpit,andreasn/cockpit,moraleslazaro/cockpit,garrett/cockpit,cockpit-project/cockpit,andreasn/cockpit,cockpit-project/cockpit,cockpituous/cockpit,deryni/cockpit,cockpituous/cockpit,cockpituous/cockpit,deryni/cockpit,cockpituous/cockpit,deryni/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,moraleslazaro/cockpit