Added apis to scenario manager

Tempest plugins do use associate_floating_ip() and
disassociate_floating_ip() api but scenario-
manager doesn't implement it.
The plugins using these apis are manila-tempest-
plugin, tap, vmware-nsx and neutron-tempest-plugin.
Hence, added it to the scenario manager

Implements: blueprint tempest-scenario-manager-stable
Signed-off by: Soniya Vyas<svyas@redhat.com>
Change-Id: I41792bdc3478f5f290a6b3b7172ef3f6b4c62c19

releasenotes/notes/associate-disassociate-floating_ip-0b6cfebeef1304b0.yaml

@@ -0,0 +1,5 @@
+---
+features:
+  - |
+    Added associate_floating_ip() and dissociate_floating_ip() methods
+    to the scenario manager.

tempest/scenario/manager.py

@@ -1137,6 +1137,32 @@ class NetworkScenarioTest(ScenarioTest):
                         floating_ip['id'])
         return floating_ip
 
+    def associate_floating_ip(self, floating_ip, server):
+        """Associate floating ip
+
+        This wrapper utility attaches the floating_ip for
+        the respective port_id of server
+        """
+        port_id, _ = self._get_server_port_id_and_ip4(server)
+        kwargs = dict(port_id=port_id)
+        floating_ip = self.floating_ips_client.update_floatingip(
+            floating_ip['id'], **kwargs)['floatingip']
+        self.assertEqual(port_id, floating_ip['port_id'])
+        return floating_ip
+
+    def disassociate_floating_ip(self, floating_ip):
+        """Disassociates floating ip
+
+        This wrapper utility disassociates given floating ip.
+        :param floating_ip: a dict which is a return value of
+        floating_ips_client.create_floatingip method
+        """
+        kwargs = dict(port_id=None)
+        floating_ip = self.floating_ips_client.update_floatingip(
+            floating_ip['id'], **kwargs)['floatingip']
+        self.assertIsNone(floating_ip['port_id'])
+        return floating_ip
+
     def check_floating_ip_status(self, floating_ip, status):
         """Verifies floatingip reaches the given status