Force python-keystoneclient to version 2.3.1 for tacker to work
Force python-keystoneclient to version 2.3.1 for tacker to work

Tacker client is installed from Tim Rozet repository, it doesn't
support version 3 of the keystone client.

Change-Id: Ie2005b1590dfccf93442995e96e0c02b4629edea
Signed-off-by: jose.lausuch <a4ed9890ad7f6494ac84a749f29a4dc3449a1186@ericsson.com>

opnfv/functest,opnfv/functest,mywulin/functest,mywulin/functest