Bump src/github.com/cloudfoundry/yagnats

Bump cloudfoundry/yagnats:
  Eric Malm and Luan Santos:
     Let apcera's nats client retry infinitely ( Travis created: https://travis-ci.org/cloudfoundry/yagnats/builds/35690105 )
  Michael Fraenkel:
     Fix deprecation warning ( Travis Success: https://travis-ci.org/cloudfoundry/yagnats/builds/35686115 )