test: fix URL (#777)
test: fix URL (#777)

On CI machines the image registry is present and reachable.
That causes the actual registry, not mock server, is accessed by the test.

Signed-off-by: Matej Vasek <641136dff7ce0a7463dc13442864dad9b6842739@redhat.com>
knative/func,knative/func,knative/func,knative/func,knative/func,knative/func,knative/func