Add accurate timestamps in proxy log

Add accurate timestamps to the proxy-logging middleware log lines for
the start and end of a request. We use 9 digits of precision since on
some systems the clock resolution can be as fine as 1 ns.

The goal is to allow for log processing that can use the more accurate
timestamps to correlate requests, computing number of requests in
flight at a given historical point in time.

Change-Id: I61e8784b1c455d629f1299207fc4fc7e4a134814
Signed-off-by: Peter Portante <peter.portante@redhat.com>
Merge "Add accurate timestamps in proxy log"