Add cloud name for VCA

This will add an additional VCA configuration option
which is needed for multicloud controller support in
N2VC. This will need no changes in the installer and
will default to the same values as before.

Change-Id: Ibccc2b102f056674117b6d98c43a3c357a78f40f
Signed-off-by: Dominik Fleischmann <dominik.fleischmann@canonical.com>