Core: Cleanup in deltacloud error HAML views

* Removed all HAML views for handling errors
* Added one HAML view to handle them all

Signed-off-by: Michal fojtik <mfojtik@redhat.com>
Core: Added one error view to handle all error states

This should fix the numerous problems we have with
maintaining large list of error views. The HAML views
for errors looks all the same, so this patch should
provide consistency across all reported errors.

Signed-off-by: Michal fojtik <mfojtik@redhat.com>
TrackedAt: http://tracker.deltacloud.org/patch/8e499a8b524059285698907d92daf785e46e2ef6
Core: Corrected error message in in instances collection test

Signed-off-by: Michal fojtik <mfojtik@redhat.com>
TrackedAt: http://tracker.deltacloud.org/patch/f18b28742b50c88534a74d345a7f20b37324cdc3