Change RootFS for tcp-sample-receiver to speed up tests
Change RootFS for tcp-sample-receiver to speed up tests

  + Uses busybox:ubuntu-14.04 instead of cloudfoundry/trusty64

[Finishes #101327288]

cloudfoundry-incubator/cf-tcp-router-acceptance-tests,cloudfoundry-incubator/cf-tcp-router-acceptance-tests