Add support for API microversions in Tempest tests

This adds support for testing Ironic API microversions, specified
as an additional 'X-OpenStack-Ironic-API-Version' header. This change
also adds tests for Ironic API /v1/nodes/(node_ident)/states/*
endpoint for microversions that were changing state machine.

Co-Authored-By: Vladyslav Drok <vdrok@mirantis.com>
Change-Id: Ibf0c73aa6795aaa52e945fd6baa821de20a599e7
diff --git a/ironic_tempest_plugin/clients.py b/ironic_tempest_plugin/clients.py
index 70ce134..2cb7c73 100644
--- a/ironic_tempest_plugin/clients.py
+++ b/ironic_tempest_plugin/clients.py
@@ -28,8 +28,13 @@
 class Manager(clients.Manager):
     def __init__(self,
                  credentials=ADMIN_CREDS,
-                 service=None,
-                 api_microversions=None):
+                 service=None):
+        """Initialization of Manager class.
+
+        Setup service client and make it available for test cases.
+        :param credentials: type Credentials or TestResources
+        :param service: service name
+        """
         super(Manager, self).__init__(credentials, service)
         self.baremetal_client = BaremetalClient(
             self.auth_provider,