Correct default service_name for nova_catalog*_info config option

Correct default service_name for nova_catalog*_info config option

The default service_name in config option (nova_catalog_info and
nova_catalog_admin_info) was mistakenly put as 'nova'. Consequently,
it is impossible to invoke novaclient APIs from Cinder code without
changing the default value of those config options.

The correct service_name defined in Keystone's config file
"/etc/keystone/default_catalog.templates" is:
catalog.RegionOne.compute.name = Compute Service.

This change replaces 'nova' with 'Compute Service' for default value
of 'nova_catalog*_info' config options.

Change-Id: Idee3585a08efa1d6af1f4ee2b74e8cefb05cc54f
Closes-Bug: 1401800