Modify --endpoint-type to --os-endpoint-type for nova

We are trying to remove deprecated option:
--endpoint-type in https://review.openstack.org/#/c/317795/
so we should use --os-endpoint-type for nova now.

Change-Id: I2010424a38ba6b817235b507769893413ec27b34
diff --git a/tempest/lib/cli/base.py b/tempest/lib/cli/base.py
index 54f35f4..9460bf4 100644
--- a/tempest/lib/cli/base.py
+++ b/tempest/lib/cli/base.py
@@ -247,7 +247,7 @@
         :param merge_stderr: if True the stderr buffer is merged into stdout
         :type merge_stderr: boolean
         """
-        flags += ' --endpoint-type %s' % endpoint_type
+        flags += ' --os-endpoint-type %s' % endpoint_type
         return self.cmd_with_auth(
             'cinder', action, flags, params, fail_ok, merge_stderr)