Fixes #7522 - made CA textarea editable for oVirt/RHEV

DO NOT MERGE

I don't know why but the helper popover does not work for me. It is AJAX based
I understand but this is what I see in logs:

```
Started GET "/compute_resources/provider_selected" for 127.0.0.1 at 2014-09-18 21:32:04 +0200
Processing by ComputeResourcesController#provider_selected as JS
  User Load (0.2ms)  SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT 1  [["id", 1]]
Setting current user thread-local variable to admin
   (0.2ms)  SELECT COUNT(*) FROM "taxonomies" WHERE "taxonomies"."type" IN ('Organization')
Setting current organization thread-local variable to none
   (0.1ms)  SELECT COUNT(*) FROM "taxonomies" WHERE "taxonomies"."type" IN ('Location')
Setting current location thread-local variable to none
  AuthSource Load (0.2ms)  SELECT "auth_sources".* FROM "auth_sources" WHERE "auth_sources"."id" = 1 LIMIT 1
   (0.1ms)  SELECT id FROM "taxonomies" WHERE "taxonomies"."type" IN ('Location') LIMIT 1
   (0.1ms)  SELECT id FROM "taxonomies" WHERE "taxonomies"."type" IN ('Organization') LIMIT 1
Completed 500 Internal Server Error in 10.8ms

Foreman::Exception (ERF42-1330 [Foreman::Exception]: must provide a provider):
  app/models/compute_resource.rb:69:in `new_provider'
  app/controllers/compute_resources_controller.rb:79:in `provider_selected'
  app/models/concerns/foreman/thread_session.rb:33:in `clear_thread'
  lib/middleware/catch_json_parse_errors.rb:9:in `call'
```

Anyone?