bump gorouter
bump gorouter

Submodule src/code.cloudfoundry.org/gorouter 866aa4f..00356fd:
  > feat: drain and stop in panicCheck
  > delete: unused threading.SharedBoolean
  > refactor: health status

Co-authored-by: Mikael Manukyan <28e16665670bfec41e6fa42496ac6b4836d715ae@pivotal.io>
Co-authored-by: Cameron Moreau <bb182232047a5ea6392d4742be27991bfb9b5655@pivotal.io>

cloudfoundry-incubator/cf-routing-release,cloudfoundry-incubator/cf-routing-release,cloudfoundry-incubator/cf-routing-release