[2298] add CONST_BASETIME and use it in MockBoss and MyStats classes

Add fixed BASETIME not depending on the time module. And modify
MockBoss and MockStats classes in order that they return time values
of that. This is for testing b10-stats and b10-stats-httpd.

src/bin/stats/tests/test_utils.py

@@ -31,6 +31,8 @@ import isc.config.cfgmgr
 import stats
 import stats_httpd
 
+CONST_BASETIME = (2011, 6, 22, 8, 14, 8, 2, 173, 0)
+
 class SignalHandler():
     """A signal handler class for deadlock in unittest"""
     def __init__(self, fail_handler, timeout=20):
@@ -237,7 +239,7 @@ class MockBoss:
   }
 }
 """
-    _BASETIME = (2011, 6, 22, 8, 14, 8, 2, 173, 0)
+    _BASETIME = CONST_BASETIME
 
     def __init__(self):
         self._started = threading.Event()
@@ -472,6 +474,11 @@ class MockAuth:
         return isc.config.create_answer(1, "Unknown Command")
 
 class MyStats(stats.Stats):
+
+    stats._BASETIME = CONST_BASETIME
+    stats.get_timestamp = lambda: time.mktime(CONST_BASETIME)
+    stats.get_datetime = lambda x=None: time.strftime("%Y-%m-%dT%H:%M:%SZ", CONST_BASETIME)
+
     def __init__(self):
         self._started = threading.Event()
         stats.Stats.__init__(self)