fix: should mark fetching status as timeout when disconnect

[yangby-cryptape]

I updated the test to reproduce this bug.

You can rebase the commit, and update the last 2 assert with your bugfix.

With your bugfix:

-     assert_eq!(peers.get_txs_to_fetch().len(), 0);
-     assert_eq!(peers.get_headers_to_fetch().len(), 0);
+     assert_eq!(peers.get_txs_to_fetch().len(), 1);
+     assert_eq!(peers.get_headers_to_fetch().len(), 1);

p.s. I tested in my laptop.