Update module calling un-loaded functions - causing errors

Issue Summary

Drupal 7.9 - OpenPublish 7.x-1.0.2
nginx Barracuda/1.0.10
PHP 5.2.17
Aegir

I was running into issues with the OpenPublish apps installer which uses the update module. My use case and errors are listed in this issue: Installing Disqus "app" - AJAX HTTP error

However, once I hacked OpenPublish to work, I realized there were other errors occurring in the update.manager.inc. Some functions in update.manager.inc were calling _update_manager_XXX helper functions that weren't available but live in the update.module file. In particular the update_manager_file_get() function calls _update_manager_cache_directory() but that helper function isn't loaded from upload.module.

I will attach a patch that is my attempt to move these helper functions to the upload.manager.inc and adjusts the upload.module to load them only when necessary. Hopefully this makes sense.