Define 'links' as a common parameter type

Nova APIs contain a lot of 'links' parameter and the definitions of
each API are the same. This patch adds a common type for 'links' and
shares it between APIs for the maintenancebility.

Partially implements blueprint nova-api-attribute-test

Change-Id: I9609a9cadb0a7edd707fe57e76b3d629a0b3f8bc
4 files changed