bump silk
bump silk

Submodule src/code.cloudfoundry.org/silk 9634c814..06f5b0a9:
  > Make test less flakey

Signed-off-by: Joachim Valdez <f4115f6bcd6858c277581a1d9da83b9914dce2c3@us.ibm.com>

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