modify old naming testcase_base to testcase
modify old naming testcase_base to testcase

testcase_base is the old naming, now testcase is adopted

Change-Id: Ic937da1fba16060d8a2ff1e6f3d1301be1293cd3
Signed-off-by: SerenaFeng <382e42c9362c05401b97e548e66ecc0826ab4b31@zte.com.cn>

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