Adding some methods on functest_utils.py
Adding some methods on functest_utils.py

These methodes allow to manage :
- keystone user, tenant and role
- glance image
- nova flavor

These methodes will be used on vIMS test-case.

JIRA: FUNCTEST-38

Change-Id: Ib5f1fb5ef325ab0527115a36b9c6ce6b45aa84f6
Signed-off-by: boucherv <64fdbde26d79357f2ea4ec922495f66daec55a90@live.fr>

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