Fix random import error when running scripts

[JamesHutchison]

Addresses #2609

The underlying issue seemed to be some inconsistency with __initialized__ and __initializing__ variables. I'm under the impression these are both Brython internals.

It's possible these were separated on purpose.

I think the "from" import is potentially incorrect, or at least could be reorganized to make its intent clearer, but it looks like simply updating everything to __initialized__ fixed the VFS issue I was seeing. It's probably hiding an issue with the logic.

I also changed the logic to what I thought it was trying to do and found that lazy (file based, not VFS) imports broke (see the revert here: 6a6a678)

I'm guessing this logic is important to keep as-is but didn't look into why. Having it also check for __file__ breaks this:

                try{
                    __path__ = $B.$getattr($B.imported[_mod_name], "__path__")
                }catch(e){
                    // If this is the last but one part, and the last part is
                    // an attribute of module, and this attribute is a module,
                    // return it. This is the case for os.path for instance
                    if(i == len - 1 &&
                            $B.imported[_mod_name][parsed_name[len]] &&
                            $B.imported[_mod_name][parsed_name[len]].__class__ ===
                                $B.module){
                        return $B.imported[_mod_name][parsed_name[len]]
                    }