Bug fixes and x-trans-id plumbing.

Fixed bug in reporting where per-size stats per operation type were
using the "all sizes" data.

Fixed bug in GET where last_byte_latency was being calculated before
actually reading the data out of the socket (so it was inaccurately
low).  We can now pass swift_client.get_object a toss_body=True
parameter which tells it to sink object contents itself, calculating the
last-byte-latency correctly.

Some operations cannot get a meaningful first-byte-latency, so they
don't; this is now correctly reported as "N/A".  CREATE and UPDATE
*could* get a first-byte-latency if we had an HTTP library which
correctly handled Expect: 100-continue and the 100 Continue response
(but we do not).

Each result's Swift X-Trans-Id header is now included in the result in
the trans_id key.  We don't do anything with these yet, but we'll
eventually report the top N slowest operations and their X-Trans-Id for
troubleshooting based on benchmark results.

Increased precision in report data (they're now visible down to three
decimal places, or milliseconds).

Fixed bug in ssbench-master report-scenario where --quiet (only
available and sensible for run-scenario) caused trouble.
Get tests passing again.