fix: rest - set self.start from client.start

Make elasped time include time since client was initialized.

So elapsed is as close as we can get to an overall request service
time.

May need to add rest_elapsed or some other subsystem based timers as
we try to track a possible performance regression in 2.3.0.

Author: rouilj

roundup/rest.py

@@ -433,7 +433,7 @@ def __init__(self, client, db):
         self.db = db
         self.translator = client.translator
         # record start time for statistics reporting
-        self.start = time.time()
+        self.start = client.start
         # disable stat reporting by default enable with @stats=True
         # query param
         self.report_stats = False