bug fix: duplicate start_date var with different type
bug fix: duplicate start_date var with different type

mix between the var and its display value leads to problem when
pushing the results to the DB

Change-Id: I582785f38f35add1251b58491843b4f3f20a3ff8
Signed-off-by: Morgan Richomme <863ecccd07b4194c40ddc432b982c8c67e56599a@orange.com>

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