Prevent the migration of VM with 'optimize' False in VM metadata

This patch adds the functionality to filter out VMs which have
metadata field 'optimize' set to False. This patch implements the
functionality for basic_consolidation strategy.

Change-Id: Iaf7b63e09534e4a67406e7f092242558b78c0bde
Partially-Implements: BP audit-tag-vm-metadata

watcher/decision_engine/model/element/instance.py

@@ -48,7 +48,7 @@ class Instance(compute_resource.ComputeResource):
         "disk": wfields.IntegerField(),
         "disk_capacity": wfields.NonNegativeIntegerField(),
         "vcpus": wfields.NonNegativeIntegerField(),
-        "metadata": wfields.DictField(),
+        "metadata": wfields.JsonField(),
     }
 
     def accept(self, visitor):

watcher/decision_engine/model/model_root.py

@@ -235,3 +235,10 @@ class ModelRoot(nx.DiGraph, base.Model):
                 model.add_instance(instance)
 
         return model
+
+    @classmethod
+    def is_isomorphic(cls, G1, G2):
+        def node_match(node1, node2):
+            return node1.as_dict() == node2.as_dict()
+        return nx.algorithms.isomorphism.isomorph.is_isomorphic(
+            G1, G2, node_match=node_match)