Update to Xtesting 0.56
Update to Xtesting 0.56

Change-Id: Ia7eb5f6c7448bcd760ebb19e2ad66ba183242e83
Signed-off-by: Cédric Ollivier <d48310251a4a484d041bc5d09a9ac4d86d20f793@orange.com>

opnfv/functest,opnfv/functest