Exchange Scaling Tests to find bottleneck

[sf2ne]

• fix the current scale tests to work with updated exchange code
• Run hzn register ... against your locally running exchange so you can look at the log and get a list of the exact exchange rest api calls it makes for a registration. (In this environment, your node will never get an agreement, but the hzn register cmd should complete.)
• Build scale tests using just the api calls made for hzn register ... (this is being handled in Bruce's issue)