Fix test case for updating volume type extra specs

The create_volume_type_extra_specs API in volume types_client actually
contains both 'create' and 'update' function for extra specs of a volume
type. The 'update' function not only can update volume type's existing
extra specs, but also can add new extra specs to the volume type. This
patch adds test for this 'update' function.

Change-Id: Iaa7c760920267c7db58650fc120e8c9033e875d7
1 file changed