tests-extra: Fixed wrong map() usage in test.

tests-extra/tests/dnssec/add_remove/test.py

@@ -14,6 +14,7 @@ def update_zone(master, slave, zone, changes, change_serial=False, serials=None)
         if change_serial:
             # update zone serial to one given in the 'serials' list
             master.zones[zone[0].name].zfile.update_serial(serials[i])
+            serial = serials[i]
         else:
             serials.append(serial)
         master.reload()
@@ -34,7 +35,8 @@ def do_steps(master, slave, zone):
     rev = list(range(1, CHANGE_COUNT + 1))
     rev.reverse()
     # increase serials so that server accepts them
-    map(lambda x: x + 1000, serials)
+    serials = list(map(lambda x: x + 1000, serials))
+    serials.reverse()
     update_zone(master, slave, zone, rev[1:], change_serial=True, serials=serials)
 
 t = Test()