0 bytes payload breaks MPerf

In MPerf, if the user sets the payload of the message to be 0 bytes, MPerf breaks and returns some strange results. The message size that is being set from MPerf is the payload size. If the payload is 0 bytes, then further headers added to the message will increase the size of the message (i.e will not be zero). All the calculations in MPerf are based on the payload size and the headers size are ignored. For example, on a single physical node with one MPerf instance open sending 10000 messages, the following results are returned:

Average/node: 0 msgs, 0b received, time=1396968184880ms, msgs/sec=0, throughput=0.0b
Average/cluster: 0 msgs, 0b received, time=1396968184880ms, msgs/sec=0, throughput=0.0b