Fix incorrect project path warning after failed project path rename

If an update to the project path fails validation, the unsaved attributes would still be presented because the controller would fall through and call render on the unsaved object. This resulted in the wrong project path being displayed in the "Delete project" warning. However, unlike with !40353 (merged), changes in Project#to_param in ea4d6c87 prevented the wrong project path from being deleted.

While it may have been intentional to retain the failed values, it's better to be safe and reset all the values back to their persisted state.

Relates to #241110 (closed)