Fix resetting backends.

moto/core/models.py

@@ -234,14 +234,12 @@ class BaseModel(object):
 class BaseBackend(object):
 
     def reset(self):
+        for service, models in model_data.items():
+            for model_name, model in models.items():
+                model.instances = []
         self.__dict__ = {}
         self.__init__()
 
-    def get_models(self):
-        import pdb;pdb.set_trace()
-        models = getattr(backend.__class__, '__models__', {})
-
-
     @property
     def _url_module(self):
         backend_module = self.__class__.__module__

moto/ec2/models.py

@@ -2633,7 +2633,7 @@ class VPCGatewayAttachment(BaseModel):
 
     @property
     def physical_resource_id(self):
-        return self.id
+        return self.vpc_id
 
 
 class VPCGatewayAttachmentBackend(object):