Updated rcperf/tx_async_multiread to be more efficient.
Updated rcperf/tx_async_multiread to be more efficient.

Moved the stack allocation of things to outside the sample loop.

ellitron/RAMCloudTools,jdellithorpe/RAMCloudTools,ellitron/RAMCloudTools,jdellithorpe/RAMCloudUtils,ellitron/RAMCloudTools,jdellithorpe/RAMCloudUtils,jdellithorpe/RAMCloudTools,jdellithorpe/RAMCloudUtils