fix flex e2e test (#857)
fix flex e2e test (#857)

Signed-off-by: Wayne Zhang <bc786b8a4d6362cffdb954a38777b93c3461fd92@google.com>
cloudendpoints/esp,cloudendpoints/esp,cloudendpoints/esp,cloudendpoints/esp,cloudendpoints/esp,cloudendpoints/esp,cloudendpoints/esp,cloudendpoints/esp