improvements for the stream tests
improvements for the stream tests

* spawn jobs in parallel
* test powers of 2 (starting at 0, 1, ..., up to 128)
* log each sampling total duration
* set GOMAXPROCS
* atomically increase received bytes

shashidharatd/garden-linux,tsaleh/garden,tangfeixiong/garden,cloudfoundry-incubator/garden-linux,tsaleh/garden,cloudfoundry-incubator/garden,savaki/garden,shashidharatd/garden-linux,cloudfoundry-incubator/garden-linux,savaki/garden,shashidharatd/garden-linux,cloudfoundry-incubator/garden,tangfeixiong/garden,shashidharatd/garden-linux,cloudfoundry-incubator/garden-linux