bump silk
bump silk

Submodule src/code.cloudfoundry.org/silk 3d8686f3..8dcb010b:
  > Instrument silk-controller main with a bit more logging

cloudfoundry-incubator/cf-networking-release,cloudfoundry-incubator/cf-networking-release,cloudfoundry-incubator/cf-networking-release,cloudfoundry-incubator/cf-networking-release