Integration tests in Docker can fill up disk

[jbarrick-mesosphere]

What happened:

My integration tests running in Docker ran out of disk space:

coverage: 76.0% of statements
ok  	github.com/kudobuilder/kudo/pkg/kudoctl/bundle	0.044s	coverage: 76.0% of statements
?   	github.com/kudobuilder/kudo/pkg/kudoctl/bundle/finder	[no test files]
# go.uber.org/zap/internal/exit
vet: failed to write analysis facts: open $WORK/b593/vet.out: no space left on device
# k8s.io/client-go/plugin/pkg/client/auth/gcp
vet: failed to write analysis facts: open $WORK/b576/vet.out: no space left on device
# github.com/kudobuilder/kudo/pkg/kudoctl/util/kudo.test
/usr/local/go/pkg/tool/linux_amd64/link: flushing $WORK/b563/kudo.test: write $WORK/b563/kudo.test: no space left on device
# github.com/kudobuilder/kudo/pkg/test/utils.test
/usr/local/go/pkg/tool/linux_amd64/link: flushing $WORK/b570/utils.test: write $WORK/b570/utils.test: no space left on device

I was running them in a loop and we do not run the Docker container with --rm so every container stays around.