Use base_physnet plugin in Ironic Inspector

Since Ussuri, Ironic Inspector contains a base_physnet plugin that was
based on the one in this repository. This change switches to use that
plugin and deletes the one in this repository.

This also fixes an issue caused by a change in the Ironic client:

    Unexpected exception during processing: TypeError: get_client() got
    an unexpected keyword argument 'api_version'

Fixes: #11

stackhpc_inspector_plugins/plugins/ib_physnet.py

@@ -16,7 +16,7 @@
 from ironic_inspector import utils
 from oslo_config import cfg
 
-from stackhpc_inspector_plugins.plugins import base_physnet
+from ironic_inspector.plugins import base_physnet
 
 LOG = utils.getProcessingLogger(__name__)
 

stackhpc_inspector_plugins/plugins/system_name_physnet.py

@@ -17,7 +17,7 @@
 from ironic_inspector import utils
 from oslo_config import cfg
 
-from stackhpc_inspector_plugins.plugins import base_physnet
+from ironic_inspector.plugins import base_physnet
 from stackhpc_inspector_plugins import utils as sip_utils
 
 LOG = utils.getProcessingLogger(__name__)