fix unbound variable
fix unbound variable

Running

    ./setup-prow-components.sh -build=fakegcsserver -delete=fakegcsserver

resulted in

    ./setup-prow-components.sh: line 143: fakepubsub_node_port: unbound variable

so we fix it by providing a default. The `deploy_prow` function already
did this, so we move the defaulting logic to the outer callsite.

cblecker/test-infra,michelle192837/test-infra,jessfraz/test-infra,cjwagner/test-infra,cjwagner/test-infra,cjwagner/test-infra,jessfraz/test-infra,michelle192837/test-infra,cjwagner/test-infra,dims/test-infra,dims/test-infra,BenTheElder/test-infra,BenTheElder/test-infra,BenTheElder/test-infra,kubernetes/test-infra,dims/test-infra,cblecker/test-infra,michelle192837/test-infra,michelle192837/test-infra,jessfraz/test-infra,dims/test-infra,cblecker/test-infra,michelle192837/test-infra,kubernetes/test-infra,jessfraz/test-infra,cblecker/test-infra,jessfraz/test-infra,dims/test-infra,cblecker/test-infra,BenTheElder/test-infra,cjwagner/test-infra,dims/test-infra,BenTheElder/test-infra,kubernetes/test-infra,jessfraz/test-infra,michelle192837/test-infra,cblecker/test-infra,cjwagner/test-infra,kubernetes/test-infra,kubernetes/test-infra,BenTheElder/test-infra,kubernetes/test-infra