Fix Error 500 after renaming a project path
Renaming the path of a project would result in an Error 500 due to `@repository` being memoized with the old path. An Error 500 would result:
```
Started GET "/testing2/test1" for 127.0.0.1 at 2016-04-04 12:42:30 +0000
Processing by ProjectsController#show as HTML
Parameters: {"namespace_id"=>"testing2", "id"=>"test1"}
Completed 200 OK in 637ms (Views: 194.2ms | ActiveRecord: 111.8ms)
Started GET "/testing2/test1/edit" for 127.0.0.1 at 2016-04-04 12:42:33 +0000
Processing by ProjectsController#edit as HTML
Parameters: {"namespace_id"=>"testing2", "id"=>"test1"}
Completed 200 OK in 594ms (Views: 183.8ms | ActiveRecord: 87.4ms)
Started PATCH "/testing2/test1" for 127.0.0.1 at 2016-04-04 12:42:41 +0000
Processing by ProjectsController#update as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"[FILTERED]", "project"=>{"nam
e"=>"test123", "path"=>"test123"}, "namespace_id"=>"testing2", "id"=>"test1"}
Completed 500 Internal Server Error in 1852ms (ActiveRecord: 124.0ms)
ActionView::Template::Error (no repository for such path):
2: %legend
3: Builds:
4:
5: - unless @repository.gitlab_ci_yml
6: .form-group
7: .col-sm-offset-2.col-sm-10
8: %p Builds need to be configured before you can begin using Contin
uous Integration.
app/models/repository.rb:59:in `block in empty?'
lib/repository_cache.rb:19:in `fetch'
app/models/repository.rb:59:in `empty?'
app/models/repository.rb:471:in `gitlab_ci_yml'
app/views/projects/_builds_settings.html.haml:5:in `_app_views_projects__build
s_settings_html_haml__782034335636359229_73397600'
app/views/projects/edit.html.haml:87:in `block in _app_views_projects_edit_htm
l_haml___2388082585934859365_47390860'
app/views/projects/edit.html.haml:8:in `_app_views_projects_edit_html_haml___2
388082585934859365_47390860'
app/controllers/projects_controller.rb:54:in `block (2 levels) in update'
app/controllers/projects_controller.rb:43:in `update'
lib/gitlab/middleware/go.rb:16:in `call'
```
Closes#14885
See merge request !3528
779b9eac57