Expand test coverage for incident status component

See: !265 (comment 549773894)

We want to establish a proper set of test coverage for status.vue through a selection of unit tests inside tests/integration/components/status_spec.js.

Our test coverage plan should cover:

1. Does the component render the correct markup?
2. Does the component render the right colours when all incidents are closed?
3. Does the component render the right colours when some incidents are open?

State 1	State 2