checkRestoreAcrossPack(): A live storage iterator keeps the file open,

which makes it impossible for teardown to delete the file on Windows,
which causes this test to fail, and also "the next" test to fail because
its setup can't delete Source.fs either.  So explictly close the storage
iterator.

src/ZODB/tests/RecoveryStorage.py

@@ -145,10 +145,12 @@ class RecoveryStorage(IteratorDeepCompare):
 
         # copy the final transaction manually.  even though there
         # was a pack, the restore() ought to succeed.
-        final = list(self._storage.iterator())[-1]
+        it = self._storage.iterator()
+        final = list(it)[-1]
         self._dst.tpc_begin(final, final.tid, final.status)
         for r in final:
             self._dst.restore(r.oid, r.serial, r.data, r.version, r.data_txn,
                               final)
+        it.close()
         self._dst.tpc_vote(final)
         self._dst.tpc_finish(final)