discovery: optional support for testing changing driver

Now that we have reset_interfaces in the API, we can try changing the driver after
discovery. This is optional, since reset_interfaces was only introduced in Rocky.

Change-Id: I8718941bb194c8fc0646a1f0bc11ef3468291ccb
diff --git a/ironic_tempest_plugin/config.py b/ironic_tempest_plugin/config.py
index 7cabf69..a3b5019 100644
--- a/ironic_tempest_plugin/config.py
+++ b/ironic_tempest_plugin/config.py
@@ -195,4 +195,7 @@
                default='fake',
                help="The driver expected to be set on newly discovered nodes. "
                     "Only has effect with auto_discovery_feature is True."),
+    cfg.StrOpt('auto_discovery_target_driver',
+               help="The driver to set on the newly discovered nodes. "
+                    "Only has effect with auto_discovery_feature is True."),
 ]