The tempest configuration function did not inject all account
details in tempest.conf. The only reason why it worked, was
because tempest uses default config values which are valid for
the current devstack setup.
To remove this dependency, two patches are needed:
- this one in devstack, to inject all values
- https://review.openstack.org/#/c/77602/ in tempest, to change
default values to None
Partially fixes bug 1287191
Change-Id: I01507b142703a1ff66707464b9a743e9d0ca3e01