Bump src/executor, src/nsync, src/warden-linux

Bump cloudfoundry-incubator/executor:
  Amit Gupta:
     switch to dropsonde log emitter ( Travis Success: https://travis-ci.org/cloudfoundry-incubator/executor/builds/34448652 )
  Ted Young:
     Always sync registry with warden ( Travis Failed: https://travis-ci.org/cloudfoundry-incubator/executor/builds/34445480 )
     Bump lager ( Travis Success: https://travis-ci.org/cloudfoundry-incubator/executor/builds/34443620 )
     Clean up logging in depot client ( Travis Unknown )
Bump cloudfoundry-incubator/nsync:
  Amit Gupta:
     Lock etcd in scripts/test ( Travis Success: https://travis-ci.org/cloudfoundry-incubator/nsync/builds/34740272 )
  Abhijit Hiremagalur:
     Bump runtime-schema for addition of staging_metadata ( Travis Failed: https://travis-ci.org/cloudfoundry-incubator/nsync/builds/34735767 )
Bump cloudfoundry-incubator/warden-linux:
  Amit Gupta:
     fix flaky logging test
     Delete cgroups inside cgroups when deleting containers. [finishes #78086354]
  Alex Suraci:
     when stracing, capture longer string lengths
     ignore SIGPIPE in wsh