return Integer instead of int

Author: yyyyx4

src/sage/groups/additive_abelian/additive_abelian_group.py

@@ -352,7 +352,7 @@ def exponent(self):
             1
         """
         if not self.invariants():
-            return 1
+            return ZZ(1)
         else:
             ann =  self.annihilator().gen()
             if ann: