Fix provision_encap.py to be able to set the Keystone tenant

Change-Id: I7648dc3c3da8a33fd602096f831653de7c7bdf84
Signed-off-by: Édouard Thuleau <edouard.thuleau@cloudwatt.com>
(cherry picked from commit 45161bbb990a15c19ab8599b69be1cc1e7fc07d9)
Merge "Fix provision_encap.py to be able to set the Keystone tenant" into R1.06