using system level urllib3 if not preent in requests package
using system level urllib3 if not preent in requests package

Some requests packages have their own urllib3 package bundled but some others
don't. Need to take care of both the cases
Closes-Bug: #1689675
Closes-Bug: #1691603
Change-Id: Ia88e5e110544e8f4c2a3ac2dc5b72ed0fa0d087b
(cherry picked from commit b866f7937808ec6fd71f0f878d83b37927f097e3)

nischalsheth/contrail-controller,eonpatapon/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,nischalsheth/contrail-controller,nischalsheth/contrail-controller,nischalsheth/contrail-controller,nischalsheth/contrail-controller,eonpatapon/contrail-controller,rombie/contrail-controller,nischalsheth/contrail-controller,eonpatapon/contrail-controller,nischalsheth/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,eonpatapon/contrail-controller,eonpatapon/contrail-controller,eonpatapon/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,nischalsheth/contrail-controller,eonpatapon/contrail-controller