Fix function get_hypervisors in openstack utils
Fix function get_hypervisors in openstack utils

JIRA: FUNCTEST-99

Change-Id: I23fd3fae08255d36ec158e5a522640615b5d8a10
Signed-off-by: jose.lausuch <a4ed9890ad7f6494ac84a749f29a4dc3449a1186@ericsson.com>

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