Disable set -u when sourcing dib venv
Disable set -u when sourcing dib venv

Sourcing the venv fails when we are set -u.

Change-Id: I8f1c98c2102737c75fd611059c68cccc436fcb64

dongwenjuan/project-config,openstack-infra/project-config,Tesora/tesora-project-config,dongwenjuan/project-config,openstack-infra/project-config,Tesora/tesora-project-config