Bump flask from 1.0.3 to 1.1.1 (#745)

Bump [flask](https://github.com/pallets/flask) from 1.0.3 to 1.1.1.
- [Release notes](https://github.com/pallets/flask/releases)
- [Changelog](https://github.com/pallets/flask/blob/master/CHANGES.rst)
- [Commits](https://github.com/pallets/flask/compare/1.0.3...1.1.1)

http_service/requirements.txt

@@ -2,7 +2,7 @@ apispec-webframeworks==0.4.0
 apispec[yaml]==2.0.0
 flask-apispec==0.8.0
 flask-cors
-Flask==1.0.3
+Flask==1.1.1
 gunicorn==19.9.0
 marshmallow==2.19.5
 rq-dashboard==0.5.2