OpenStack: add custom parameters for the client

* The instantiation of the novaclient Client might require additional
  parameters based on the specific OpenStack installation, like for
  example a region_name.
* Add a generic 'client_params' section to the configuration to
  allow to set arbitrary additional parameters that will be passed to
  the novalicent's Client.

Bug: T201881
Change-Id: I972b6b7326ddac2e01e39d7053e938bd33bd4ae8

cumin/backends/openstack.py

@@ -73,11 +73,13 @@ def _get_nova_client(config, project):
         novaclient.client.Client: the novaclient Client instance, already authenticated.
 
     """
+    params = config.get('client_params', {})
     return nova_client.Client(
         config.get('nova_api_version', '2'),
         session=_get_keystone_session(config, project),
         endpoint_type='public',
-        timeout=config.get('timeout', 10))
+        timeout=config.get('timeout', 10),
+        **params)
 
 
 class OpenStackQuery(BaseQuery):

doc/examples/config.yaml

@@ -27,6 +27,9 @@ openstack:
     domain_suffix: openstack.local  # OpenStack managed domain, to be added to all hostnames
     nova_api_version: 2.12
     timeout: 2  # Used for both Keystone and Nova API calls
+    # Additional parameters to set when instantiating the novaclient Client
+    client_params:
+        region_name: region1
     # Default query parameters. The ones set by default anyway are: status: ACTIVE and vm_state: ACTIVE [optional]
     query_params:
         project: project_name  # Parameter name: parameter value