java: Update PingPongApp to get new Java benchmarks

w/o proxy (LAN): ~170-200ms per ping pong iteration
w/  proxy (RPC through proxy in Central US): ~600-700ms

This latency has reduced (we cut the gen vector more often and don't
need to wait for a sync watcher poll loop). It used to be:
w/o proxy: 435-490ms
w/  proxy: 996-1098ms

Note: Go w/o proxy is 50ms. Unsure how much with the proxy, but it is
expected that we add ~450-500ms (6 RPCs * 75-80ms latency via proxy).

Change-Id: Ic62478634ed06e9dcd133460e7d0d8a5e08f6944
2 files changed