kubernetes: `update-bazel` should FAIL if it encounters "cannot find package"

verify-release-1.5 job is consistently failing “verify-bazel” on the release-1.5 branch. See https://k8s-gubernator.appspot.com/builds/kubernetes-jenkins/logs/ci-kubernetes-verify-release-1.5/

Error:

...
W1115 12:23:39.907] wrote BUILD for "/go/src/k8s.io/kubernetes/test/e2e/framework"
W1115 12:23:40.004] wrote BUILD for "/go/src/k8s.io/kubernetes/test/e2e_node"
W1115 12:23:40.485] wrote BUILD for "/go/src/k8s.io/kubernetes/test/integration/framework"
W1115 12:23:40.522] wrote BUILD for "/go/src/k8s.io/kubernetes/test/integration/scheduler_perf"
W1115 12:23:41.077] wrote BUILD for "/go/src/k8s.io/kubernetes/federation/pkg/dnsprovider/providers/google/clouddns"
W1115 12:23:41.630] wrote BUILD for "/go/src/k8s.io/kubernetes/federation/pkg/kubefed/init"
I1115 12:23:41.697] 
I1115 12:23:41.698] BUILD files are not up to date
I1115 12:23:41.698] Run ./hack/update-bazel.sh
I1115 12:23:41.699] FAILED   hack/make-rules/../../hack/verify-bazel.sh	30s

I did a fast-forward on the release-1.5 branch on Nov 14 6 PM PST. See logs here.

Looks like the update-bazel step succeed even though it was silently failing:

Updating bazel
extract err: cannot find package "cloud.google.com/go/internal" in any of:
	/usr/local/google/home/saadali/.gimme/versions/go1.7.linux.amd64/src/cloud.google.com/go/internal (from $GOROOT)
	/usr/local/google/home/saadali/go/src/cloud.google.com/go/internal (from $GOPATH)
extract err: cannot find package "github.com/Azure/go-autorest/autorest" in any of:
	/usr/local/google/home/saadali/.gimme/versions/go1.7.linux.amd64/src/github.com/Azure/go-autorest/autorest (from $GOROOT)
	/usr/local/google/home/saadali/go/src/github.com/Azure/go-autorest/autorest (from $GOPATH)
extract err: cannot find package "github.com/Azure/go-autorest/autorest/azure" in any of:
	/usr/local/google/home/saadali/.gimme/versions/go1.7.linux.amd64/src/github.com/Azure/go-autorest/autorest/azure (from $GOROOT)
	/usr/local/google/home/saadali/go/src/github.com/Azure/go-autorest/autorest/azure (from $GOPATH)
...
extract err: cannot find package "k8s.io/client-go/pkg/util/diff" in any of:
	/usr/local/google/home/saadali/.gimme/versions/go1.7.linux.amd64/src/k8s.io/client-go/pkg/util/diff (from $GOROOT)
	/usr/local/google/home/saadali/go/src/k8s.io/client-go/pkg/util/diff (from $GOPATH)
wrote BUILD for "/usr/local/google/saadali/branchff-release-1.5/kubernetes/federation/pkg/kubefed/init"
Update scripts completed successfully
OK(B

I will fix the 1.5 release branch but this bug is to make sure that update-bazel is modified to fail if it encounters “cannot find package” errors.

CC @mikedanese @kubernetes/test-infra-maintainers