In order to get a reliable and testable update environment, any code which invokes a hook during an update function is no longer allowed in Drupal 8. (Previously in Drupal 7, it was discouraged but not disallowed.)
If any code which invokes a hook is called from within an update function, Drupal 8 will throw an exception. (In addition, code which tries to disable or uninstall a module from within an update function will throw an exception, althoughmay eventually remove this restriction.)
If you need to call an API function from within an update function and the API function invokes hooks, you should instead write an update-specific version of the function and call that instead. See the documentation on Update versions of API functions for more details.