Utility functions for building test images

These functions allow images to be built using diskimage-builder which
contain packages built from local project checkouts:
build_dib_pip_repo() - Builds a local pip repo from local projects and configures
                       apache to serve it
disk_image_create_upload() - Creates and uploads a diskimage-builder built image

The unused function lib/heat disk_image_create has been deleted.

Change-Id: Ia75c7c35bfd48dbe6ae3cb9c3241de0b598cbf84
Merge "Utility functions for building test images"