substitue misused variable 'total_success' with 'success_rate'
substitue misused variable 'total_success' with 'success_rate'

JIRA: FUNCTEST-390

Change-Id: I35a2f72016573fc9e0a8403e436d5568937c5b14
Signed-off-by: SerenaFeng <382e42c9362c05401b97e548e66ecc0826ab4b31@zte.com.cn>

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