bump bbs
bump bbs

[finishes #115611661]

Submodule src/github.com/cloudfoundry-incubator/bbs 6c8e88a..de85e11:
  > Document the public LRP API

Signed-off-by: Andrew Edgar <cc1cbeb507c6357651b55d7c7887132c42e42341@ca.ibm.com>

cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release