Add test for get_instance_disk_info to test_virt_drivers

Commit 2bed16c89356554a193a111d268a9587709ed2f7 added
get_instance_disk_info to the base ComputeDriver class
but didn't add a test for it in test_virt_drivers, so
it's added here.

This also fixes the wrong method signature in the fake
virt driver.

Note that this wouldn't have found the problem for the
hyperv or vmware drivers due to bug 1209421.

Change-Id: I5765720d8c3e0a7962b493fa49359514f3136544
Related-Bug: #1358719
Fix test_create_instance_invalid_key_name

In test_create_instance_invalid_key_name, there were the duplicated
negative factors. One is nonexistent image-id, the other one is non-
existent keypair.
This patch removes nonexistent image-id for the test purpose.

Change-Id: I90ff4e9ca0eeb149aa0db7be2d171561586724e9
Add plan for kilo blueprints: project priorities

At the nova mid-cycle we agreed that while specs have made our blueprint
process significantly better, we think the current approach still leaves
much to be desired. This document is the outcome of the discussion at
the mid-cycle on how we want to manage blueprints in Kilo.

This proposal is being placed in devref, as we want to use gerrit's
workflow (two core reviews, inline comments, revisions etc) and this is
a document for developers.

Introduce the idea of project priorities.

Change-Id: I7075a130c01be22f3ee5315d4a65b8e524b5a1ad
Updated from global requirements

Change-Id: Ib184ffa042aa85b52eede765d1eb94ede96f36fa
Merge "Updated from global requirements"
Merge "Add test for get_instance_disk_info to test_virt_drivers"
Merge "Add plan for kilo blueprints: project priorities"
Merge "Fix test_create_instance_invalid_key_name"