test: Close browser when avocado finishes
test: Close browser when avocado finishes

When avocado starts its own browser it never closes it.

Since avocado tests spawn this process and it does not get cleaned up, the main
process holds stdout/err "busy" and therefore the test hangs
indefinitely.

Possibly related https://bugzilla.mindrot.org/show_bug.cgi?id=2071

Closes #11829
deryni/cockpit,garrett/cockpit,martinpitt/cockpit,deryni/cockpit,moraleslazaro/cockpit,garrett/cockpit,deryni/cockpit,moraleslazaro/cockpit,cockpituous/cockpit,garrett/cockpit,mvollmer/cockpit,cockpituous/cockpit,martinpitt/cockpit,cockpit-project/cockpit,deryni/cockpit,garrett/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,deryni/cockpit,cockpit-project/cockpit,mvollmer/cockpit,cockpituous/cockpit,deryni/cockpit,martinpitt/cockpit,cockpituous/cockpit,deryni/cockpit,martinpitt/cockpit,cockpit-project/cockpit,martinpitt/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,garrett/cockpit,mvollmer/cockpit,cockpituous/cockpit,cockpit-project/cockpit,cockpituous/cockpit,moraleslazaro/cockpit