Bump src/linux-circus, src/nsync

Bump cloudfoundry-incubator/linux-circus:
  Abhijit Hiremagalur:
     Use execution metadata when start command is not provided ( Travis Success: https://travis-ci.org/cloudfoundry-incubator/linux-circus/builds/34841892 )
Bump cloudfoundry-incubator/nsync:
  Abhijit Hiremagalur:
     Bump runtime-schema ( Travis Success: https://travis-ci.org/cloudfoundry-incubator/nsync/builds/34844914 )
     Courier metadata from CC to soldier ( Travis Failed: https://travis-ci.org/cloudfoundry-incubator/nsync/builds/34842070 )