Use time.perf_counter() for timing

`time.time()` can return a lower value than a previous call if the
system clock has been set back between the two calls.

cozy/architecture/profiler.py

@@ -7,9 +7,9 @@
 def timing(f):
     @functools.wraps(f)
     def wrap(*args):
-        time1 = time.time()
+        time1 = time.perf_counter()
         ret = f(*args)
-        time2 = time.time()
+        time2 = time.perf_counter()
         log.info('{:s} function took {:.3f} ms'.format(f.__name__, (time2-time1)*1000.0))
 
         return ret