Adds default value for fixed_key

Adds a default value for fixed_key, for use by a key manager
implementation that reads the key from the configuration settings.
This single, fixed key proffers no protection if the key is
compromised.  The current implementation of the key manager does
not work correctly if the key is not set, so including this option
is helpful for Tempest testing and volume encryption within
DevStack.

Implements: blueprint encrypt-cinder-volumes
Change-Id: Id83060afc862c793b79b5429355b213cb4c173fd
https://blueprints.launchpad.net/nova/+spec/encrypt-cinder-volumes
Update cinder cert script to use run_tempest

Changes to tempest run_tests.sh
(commit: 17520e49a7e69b3817856a739121a1fb2906f2cc)
breaks the cinder_driver_cert script. A backward
compatible run_tempest.sh script was added,
so for now we should update the cinder_driver_cert
script to use that

Change-Id: I611a01dd4788ae01da8a6167a530f9e44733dfc6
Closes-Bug: #1269531
Add missing mongodb client package on Fedora

On Fedora, when ceilometer is enabled and mongodb is used as backend,
devstack installation would fail due to missing mongodb client package.
This patch ensures the package gets installed.

Change-Id: I981bb55f86541e5ff19c52160269a7789b94423f
Merge "Add missing mongodb client package on Fedora"
Merge "Adds default value for fixed_key"
Merge "Update cinder cert script to use run_tempest"