Update to latest juju/testing.
Merge pull request #720 from howbazaar/update-juju-testing

Update to latest juju/testing.
Update blobstore rev

Fixes https://bugs.launchpad.net/juju-core/+bug/1367431
Merge pull request #722 from axw/master

Update blobstore rev

Fixes https://bugs.launchpad.net/juju-core/+bug/1367431