Add temporary aae index

Pending ct tests.  The aae index should expire after limit_minutes and
be on an index which is rounded to unit_minutes.

test/end_to_end/testutil.erl

@@ -374,7 +374,8 @@ set_object(Bucket, Key, Value, IndexGen, Indexes2Remove) ->
                                             {remove, IdxF, IdxV} end,
                                         Indexes2Remove),
             [{"MDK", "MDV" ++ Key},
-                {"MDK2", "MDV" ++ Key}]},
+                {"MDK2", "MDV" ++ Key},
+                {?MD_LASTMOD, os:timestamp()}]},
     {B1, K1, V1, Spec1, MD} = Obj,
     Content = #r_content{metadata=dict:from_list(MD), value=V1},
     {#r_object{bucket=B1,