addrman: Fix format string in deserialize error

Also add a regression test.

test/functional/test_runner.py

@@ -282,6 +282,7 @@ BASE_SCRIPTS = [
     'p2p_blockfilters.py',
     'p2p_message_capture.py',
     'feature_includeconf.py',
+    'feature_addrman.py',
     'feature_asmap.py',
     'mempool_unbroadcast.py',
     'mempool_compatibility.py',