Add back support for the multiattach flag for volume create

As the 'multiattach' request parameter in volume create is
not formally deprecated out of the REST API via microversion,
we need to keep the functionality working.

Currently the 'multiattach' attribute on the volume is set by
the volume_type only, which means that we cannot create a
multi-attach volume the old way, the volume gets created with
'multiattach': false.

This patch fixes that.

Closes-Bug: #1745219

Change-Id: Iac67f112b0dc9353c6a66e6fbc81cc8324a2b37c

cinder/tests/unit/volume/test_volume.py

@@ -628,6 +628,18 @@ def test_create_volume_with_multiattach_volume_type(self):
         self.assertEqual(foo['id'], vol['volume_type_id'])
         self.assertTrue(vol['multiattach'])
 
+    def test_create_volume_with_multiattach_no_volume_type(self):
+        """Tests creating a volume with multiattach=True but no special type.
+
+        This tests the pre 3.50 microversion behavior of being able to create
+        a volume with the multiattach request parameter regardless of a
+        multiattach-capable volume type.
+        """
+        volume_api = cinder.volume.api.API()
+        volume = volume_api.create(
+            self.context, 1, 'name', 'description', multiattach=True)
+        self.assertTrue(volume.multiattach)
+
     @mock.patch.object(key_manager, 'API', fake_keymgr.fake_api)
     def test_create_volume_with_encrypted_volume_type_aes(self):
         ctxt = context.get_admin_context()

cinder/volume/api.py

@@ -349,7 +349,8 @@ def create(self, context, size, name, description, snapshot=None,
                 # Refresh the object here, otherwise things ain't right
                 vref = objects.Volume.get_by_id(
                     context, vref['id'])
-                vref.multiattach = self._is_multiattach(volume_type)
+                vref.multiattach = (self._is_multiattach(volume_type) or
+                                    multiattach)
                 vref.save()
                 LOG.info("Create volume request issued successfully.",
                          resource=vref)