Add more port_forwarding tests

Extend set of tests for the port_forwarding feature to automate coverage
of specific cases:

  - Port forwaring on neutron ports with multiple fixed ips
  - Out of range values for port
  - Forward communication to multiple fixed IPs of a particular Neutron port
  - Editing and Deleting UDP port forwarding rule

Related-Bug: #1897753
Change-Id: I0fbf0a12c050a5a7184c96b62eee32139bc820b4
diff --git a/neutron_tempest_plugin/api/base.py b/neutron_tempest_plugin/api/base.py
index 7cf8dd4..d63dec8 100644
--- a/neutron_tempest_plugin/api/base.py
+++ b/neutron_tempest_plugin/api/base.py
@@ -702,6 +702,12 @@
         return pf
 
     @classmethod
+    def update_port_forwarding(cls, fip_id, pf_id, client=None, **kwargs):
+        """Wrapper utility for update_port_forwarding."""
+        client = client or cls.client
+        return client.update_port_forwarding(fip_id, pf_id, **kwargs)
+
+    @classmethod
     def delete_port_forwarding(cls, pf, client=None):
         """Delete port forwarding