test/run: merge verify and firefox scenarios
test/run: merge verify and firefox scenarios

The only thing separating these two is the setting of the TEST_BROWSER
environment variable, plus the NODE_ENV logic (which will now also work
for the Firefox case).

cockpit-project/cockpit,cockpit-project/cockpit,mvollmer/cockpit,martinpitt/cockpit,cockpit-project/cockpit,martinpitt/cockpit,mvollmer/cockpit,mvollmer/cockpit,mvollmer/cockpit,martinpitt/cockpit,martinpitt/cockpit,mvollmer/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,martinpitt/cockpit