Upgrade requests to version 2.20.0 to solve vulnerability alarm

Author: pcrespov

services/director/requirements/base.txt

@@ -2,5 +2,5 @@
 # Please keep alphabetical order
 aiohttp==3.3.2
 docker==3.5.0
-requests==2.19.1
+requests==2.20.0
 tenacity==4.12.0

services/storage/requirements/base.txt

@@ -15,7 +15,7 @@ passlib==1.7.1
 # See http://initd.org/psycopg/docs/install.html#binary-install-from-pypi
 psycopg2-binary==2.7.5
 python-socketio==1.9.0
-requests==2.19.0
+requests==2.20.0
 sqlalchemy==1.2.9
 tenacity==4.12.0
 trafaret-config==2.0.1

services/web/server/requirements/base.txt

@@ -17,7 +17,7 @@ minio==4.0.0
 networkx==2.1
 passlib==1.7.1
 python-socketio==1.9.0
-requests==2.19.0
+requests==2.20.0
 sqlalchemy==1.2.9
 tenacity==4.12.0
 trafaret-config==2.0.1