Add helper methods to rescue/unrescue shares

Manila is the OpenStack Shared Filesystems service.
These series of patches implement changes required in Nova to allow the shares
provided by Manila to be associated with and attached to instances using
virtiofs.

Implements: blueprint libvirt-virtiofs-attach-manila-shares
Change-Id: I0d61e0055d95b15e299ebc2b39003a9d05f29441

nova/tests/functional/integrated_helpers.py

@@ -745,6 +745,15 @@ class InstanceHelperMixin:
         server = self.api.post_server({'server': server})
         return self._wait_for_state_change(server, 'ACTIVE')
 
+    def _rescue_server(self, server):
+        self.api.post_server_action(
+            server['id'], {'rescue': {"adminPass": "MySecretPass"}})
+        return self._wait_for_state_change(server, 'RESCUE')
+
+    def _unrescue_server(self, server):
+        self.api.post_server_action(server['id'], {'unrescue': None})
+        return self._wait_for_state_change(server, 'ACTIVE')
+
 
 class PlacementHelperMixin:
     """A helper mixin for interacting with placement."""