Allow tests to run without installation

This patch makes modifications to the way that programs which the various
tests depend on are forked and executed.  This will allow the tests to be
run without installing glance to a python installation (ie: python setup.py
{develop/install} will not be needed).

fixes bug: 1197800

Change-Id: I9687cb7a5b22747d9cea0a1c24057383a8901476
Use _pre_upgrade_### instead of _prerun_###

Other projects, including nova and oslo.db, use _pre_upgrade_### as the
function to run before a DB migration test. This is to differentiate it
from the downgrade tests.

Change-Id: I0da30f7c5a1c76a7ff0e735c36b753ef7a624db9
Make size/checksum immutable for active images

Once an image becomes 'active' it should only be possible for an
administrator (and not a regular user) to change the size and checksum
values.

Addresses bug 1209148.

Change-Id: Ic65afbca4a4161dfa77ce0a296a1bd72d96902ca
Improve the error msg of v2 image_data.py

Based on current implement, the error message of some upload
failures is missing the image id. It looks like: 'Unable to
upload duplicate image data for image: %s'.

Fixes bug 1207616

Change-Id: I608fb1ba84dde0e44a73e5e1bd3e850db49d84c4
Use latest Oslo's version

The patch replaces current Oslo version with 1.2. The change is needed
to pull in a fix released in that specific version, which fixes the
issue #1175570. The fix we're interested in is giving priority to CLI
arguments instead of config files. Without this, commands like the one
below won't work.

    $ glance-manage --sql_connection=.... db_sync

Oslo's release notes:
http://docs.openstack.org/developer/oslo.config/#a3

Closes-Bug: #1175570
Change-Id: I4ea749cfaae0e18e035abe7b5d7e345dda7d476d
Merge "Make size/checksum immutable for active images"
Merge "Allow tests to run without installation"
Merge "Use _pre_upgrade_### instead of _prerun_###"
Merge "Improve the error msg of v2 image_data.py"