gateway/handlers: fix use of testing.T inside goroutine
gateway/handlers: fix use of testing.T inside goroutine

Signed-off-by: Lars Lehtonen <bfdd966b813f0bd15372a0e60134075c7206adfa@gmail.com>

alexellis/faas,alexellis/faas,alexellis/faas,alexellis/faas,alexellis/faas,openfaas/faas,openfaas/faas,alexellis/faas,alexellis/faas,openfaas/faas,alexellis/faas,alexellis/faas