Update urllib>=1.8.3

Recent commit 969bfba931f132199662851c6f309be67761c4f9 in oslo.
vmware uses urllib3 connection api's that is available only
from 1.8.3.

This patch will unblock Minesweeper CI from failing in starting
up nova-compute.

Change-Id: I861724be09ede35ecedde7537e72610ec570dcb0
Merge "Update urllib>=1.8.3"