text: Title: [RFC] Add option to skip reloading on validators.validate 
  Body: On lines
  https://github.com/rochacbruno/dynaconf/blob/master/dynaconf/validator.py#L202-L205
  
  `validators.validate` is calling `from_env` and it makes the variables to be reloaded from source files.
  
  This is not good for testing.
  
  Solution:
  
  1. Check if validation is happening on the same current env, then don't reload
  2. accept argument `reload=False` that will cause those lines to pass `settings` direct to the `validate_items`