Calculate message latency: for RPC calls on both server-side and
on client-side (round-trip); for RPC cast and NOTIFY on server-side
only.
The message is extended with metadata: sequence id, creation time,
reception time and return time (for RPC calls). For every message
the metadata is stored into MessageStatCollector. To reduce memory
consumption the collector aggregates stats on every second and can
print the ongoing stats to stdout. At the finish the overall stats
are printed.
NOTIFY tests are changed to be similar to RPC:
* use pre-generated messages
* parameter "-w WAIT_BEFORE_ANSWER" for processing delay
* parameter "--requeue" to re-queue new messages (only those that
miss the cache)
Change-Id: I4c2fc11bfaee17b6825cdc7d6edf07b8e91ef83a
84109fe8fc