Fix api-ref for project tag create
Fix api-ref for project tag create

Keystone currently returns a 201 with no body when creating a single
project tag by calling /v3/projects/{id}/tags/{value}, however the
current api documentation states that an array of tags is returned.

This is inconsistent with the current implementation which matches the
api-wg spec[0] for tags.

[0] https://specs.openstack.org/openstack/api-wg/guidelines/tags.html#addressing-individual-tags

Closes-Bug: #1756140

Change-Id: Ia15be1c79a6e8718b3613a16383ce0f5af839013

openstack/keystone,openstack/keystone,mahak/keystone,mahak/keystone,openstack/keystone,mahak/keystone