Bump src/executor, src/file-server, src/inigo, src/linux-smelter, src/stager

Bump cloudfoundry-incubator/executor:
  Onsi Fakhouri:
     Check for channel closure when handling error channel in Desired RunOnce watcher ( Travis Success: https://travis-ci.org/cloudfoundry-incubator/executor/builds/20733116 )
  David Varvel:
     log the error received when watching for run onces fails ( Travis Success: https://travis-ci.org/cloudfoundry-incubator/executor/builds/20728063 )
  Alex Suraci:
     Merge pull request #5 from fraenkel/runoncehang ( Travis Success: https://travis-ci.org/cloudfoundry-incubator/executor/builds/20703752 )
  fraenkel:
     Fix hang when cancelling after perform ( Travis Unknown )
Bump cloudfoundry-incubator/file-server:
  Alex Suraci:
     bump README
     bump demps and add drone
Bump cloudfoundry-incubator/inigo:
  David Varvel:
     bump deps, add defer GinkgoRecover()
     Spalling correction.
Bump cloudfoundry-incubator/linux-smelter:
  Onsi Fakhouri:
     fix drone build; cp behaves differently on linux vs mac
     standardize drone image
     linux-smelter runs on drone
     bump deps
Bump cloudfoundry-incubator/stager:
  Onsi Fakhouri:
     When watching for completed run onces: ( Travis Success: https://travis-ci.org/cloudfoundry-incubator/stager/builds/20733095 )
     bump deps ( Travis Success: https://travis-ci.org/cloudfoundry-incubator/stager/builds/20699361 )
     outbox handles CompletedRunOnces asynchronously ( Travis Success: https://travis-ci.org/cloudfoundry-incubator/stager/builds/20699269 )
     standardize drone image ( Travis Success: https://travis-ci.org/cloudfoundry-incubator/stager/builds/20626798 )
     bump ginkgo ( Travis Success: https://travis-ci.org/cloudfoundry-incubator/stager/builds/20626229 )