Add helper method total_seconds in timeutils.py

Almost every OpenStack project is using hardcode to calculate duration
like 'delta.days * 24 * 3600', even 2592000. Method delta_seconds takes
a timedelta instance as input to compute total seconds.

Method delta_seconds also is refactored to call new method.

Change-Id: I397bae402e012c28aaa6aa2bb10170b83eeeaa8c

openstack/common/timeutils.py

@@ -178,6 +178,15 @@ def delta_seconds(before, after):
     datetime objects (as a float, to microsecond resolution).
     """
     delta = after - before
+    return total_seconds(delta)
+
+
+def total_seconds(delta):
+    """Return the total seconds of datetime.timedelta object.
+
+    Compute total seconds of datetime.timedelta, datetime.timedelta
+    doesn't have method total_seconds in Python2.6, calculate it manually.
+    """
     try:
         return delta.total_seconds()
     except AttributeError:

tests/unit/test_timeutils.py

@@ -184,6 +184,11 @@ class TimeUtilsTest(test.BaseTestCase):
         self.assertAlmostEquals(604859.123456,
                                 timeutils.delta_seconds(before, after))
 
+    def test_total_seconds(self):
+        delta = datetime.timedelta(days=1, hours=2, minutes=3, seconds=4.5)
+        self.assertAlmostEquals(93784.5,
+                                timeutils.total_seconds(delta))
+
     def test_iso8601_from_timestamp(self):
         utcnow = timeutils.utcnow()
         iso = timeutils.isotime(utcnow)