Fix two related bugs: rescheduling periodic task + fetch manager restart of failed fetches

Apparently, posix_time::seconds() returns just seconds from [0, 59]
range and to get total number of seconds, total_seconds() call is
necessary

Change-Id: Idbc3cbd6a33e72d7f573f9cc905b73022ddf4847
diff --git a/src/fetch-manager.cc b/src/fetch-manager.cc
index e9463b7..af72e08 100644
--- a/src/fetch-manager.cc
+++ b/src/fetch-manager.cc
@@ -181,7 +181,7 @@
       item->RestartPipeline ();
     }
 
-  m_scheduler->rescheduleTaskAt (m_scheduleFetchesTask, (nextSheduleCheck - currentTime).seconds ());
+  m_scheduler->rescheduleTaskAt (m_scheduleFetchesTask, (nextSheduleCheck - currentTime).total_seconds ());
 }
 
 void