bump bytefmt
bump bytefmt

[finishes #153753954]

Submodule src/code.cloudfoundry.org/bytefmt f4415faf..a052d587:
  > Make it clear that binary-prefixed and SI prefixed units are treated the same
  > Merge remote-tracking branch 'origin/pr/16' into HEAD

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