Uses the "network_id" param creating a cluster
Uses the "network_id" param creating a cluster

This PR replaces a request parameter name "net-id" with "network_id"
creating a cluster. When creating a cluster, Clusters API internally
calls Instaces API to create a instance. A request parameter name to
create instances has changed[1] but python-troveclient still uses
old parameter name when creating a cluster.

The original problem is instance creation error when creating a
instance that belongs to a cluster. Troves's Instances API has
changed a parameter name from "net-id" to "network_id", but Clusters
API and python-troveclient still uses the "net-id" parameter name.
We need to fix it.

[1]: https://opendev.org/openstack/trove/commit/535417240709694080255c064c9d84a5ab1d5372

Task: 44925
Story: 2009958
Change-Id: Ia3d1d6f451296eba34f2389da184c41a7ee9e84e

openstack/python-troveclient,openstack/python-troveclient