Fix a ZeroDivisionError for short replicator runs.

During unittest runs it's possible for time.time() - self.start
to be zero. This patch sets the elapsed value to an arbitrarily
small number to prevent divide by zero errors.

Change-Id: I20d4b9bf7ff3cdce4e9fe3215622c01cfec7f8bb

swift/obj/replicator.py

@@ -455,7 +455,8 @@ class ObjectReplicator(Daemon):
         Logs various stats for the currently running replication pass.
         """
         if self.replication_count:
-            rate = self.replication_count / (time.time() - self.start)
+            elapsed = (time.time() - self.start) or 0.000001
+            rate = self.replication_count / elapsed
             self.logger.info(_("%(replicated)d/%(total)d (%(percentage).2f%%)"
                 " partitions replicated in %(time).2fs (%(rate).2f/sec, "
                 "%(remaining)s remaining)"),