fix(core_test): Remove test for custom CoreOS CA

This was only used by the old update service and will be removed from
our images once lingering references to it are removed.
fix(core_test): Sync with update_engine's new dbus API.

Use -status instead of whatever the url option does/did.

Just drop the dbus test for now, I tried to switch to calling GetStatus
but didn't get it working and I need to get this in and tag a release...
fix(core_test): Remove test that pings old update service.

Removing instead of updating URL because this test suite is most useful
for checking CoreOS functionality itself, not the status of the network
and remote services.
Merge pull request #29 from marineam/dbus

Fix update related tests