ensure fetch_acc is rescheduled properly when doing historic fetch

the unique flag on the task means we can't reschedule it for right now
but we must wait for the current one to end. this commit introduces a 1
second delay before the task is ran again, which should be enough

tasks.py

@@ -180,7 +180,8 @@ def fetch_acc(id_):
 
             if not account.fetch_history_complete:
                 # reschedule immediately if we're still doing the historic fetch
-                fetch_acc.apply_async((id_,))
+                print("{} is not done fetching history, resheduling.".format(account))
+                fetch_acc.apply_async((id_,), countdown=1)
 
 
     except TemporaryError: