Fix path to integrational tests
Fix path to integrational tests

Due to changes in post_test_hook.sh in mistral repository
start directory was changed to python-mistralclient
(was: functionaltests/python-mistralclient).

Change-Id: I5e2c22a14490d142da6fe2566070cc231824ebcd

StackStorm/python-mistralclient,openstack/python-mistralclient,openstack/python-mistralclient,StackStorm/python-mistralclient