Use correct status code with werkzeug exceptions

Change-Id: Ib726b7d2cc44fbea666d580d7639680bf4bfbcf1

releasenotes/notes/http-code-b4e32ad8485ef841.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    Returns the correct status code (404) when a URL is not found.

sushy_tools/emulator/main.py

@@ -167,6 +167,7 @@ def all_exception_handler(message):
         url = flask.url_for(flask.request.endpoint, identity=message.args[0])
         return flask.redirect(url, code=307, Response=flask.Response)
 
+    code = getattr(message, 'code', 500)
     if (isinstance(message, error.FishyError)
             or isinstance(message, wz_exc.HTTPException)):
         app.logger.debug(
@@ -175,7 +176,7 @@ def all_exception_handler(message):
         app.logger.exception(
             'Unexpected %s: %s', message.__class__.__name__, message)
 
-    return flask.render_template('error.json', message=message), 500
+    return flask.render_template('error.json', message=message), code
 
 
 @app.route('/redfish/v1/')