Add translation rule to delete ssh auth key from Magnum baymodel

Add a translation rule to ensure that users with existing templates will
not have them break when they update due to the 'ssh_authorized_key'
property having been removed from Magnum and hidden in Heat.

Change-Id: Id73bace93bfc2379e80777da7dc0c0bb059d6cd3
Related-Bug: #1560284

heat/engine/resources/openstack/magnum/baymodel.py

@@ -16,6 +16,7 @@ from heat.engine import constraints
 from heat.engine import properties
 from heat.engine import resource
 from heat.engine import support
+from heat.engine import translation
 
 
 class BayModel(resource.Resource):
@@ -178,6 +179,16 @@ class BayModel(resource.Resource):
 
     entity = 'baymodels'
 
+    def translation_rules(self, props):
+        if props.get(self.SSH_AUTHORIZED_KEY):
+            return [
+                translation.TranslationRule(
+                    props,
+                    translation.TranslationRule.DELETE,
+                    [self.SSH_AUTHORIZED_KEY]
+                )
+            ]
+
     def handle_create(self):
         args = {
             'name': self.properties[self.NAME],