use golang-1.13 for the tests Dockerfile
-FROM registry.svc.ci.openshift.org/ocp/builder:golang-1.12 AS builder
+FROM registry.svc.ci.openshift.org/ocp/builder:golang-1.13 AS builder
WORKDIR /go/src/github.com/openshift/origin
COPY . .
RUN make build WHAT=cmd/openshift-tests; \
