bump cfdot
bump cfdot

Submodule src/code.cloudfoundry.org/cfdot 6f8823346..929f49ee6:
  > Use MatchError matcher in locket_flags_test.go

Signed-off-by: Edwin Xie <6bc24e9c160281972837d9e13287696d26612564@pivotal.io>

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