qa: Account for errno not always being set for ConnectionResetError

Logging issue can be triggered by:

```diff
--- a/src/httpserver.cpp
+++ b/src/httpserver.cpp
@@ -263,6 +263,7 @@ std::string RequestMethodString(HTTPRequest::RequestMethod m)
 /** HTTP request callback */
 static void http_request_cb(struct evhttp_request* req, void* arg)
 {
+    throw std::runtime_error{"Hello"};
     evhttp_connection* conn{evhttp_request_get_connection(req)};
     // Track active requests
     {
```

http.client.RemoteDisconnected not specifying errno to ConnectionResetError-ctor:
https://github.com/python/cpython/blob/ce4b0ede16aea62ee7b1e02df7e1538102a356da/Lib/http/client.py#L1556C9-L1556C29

test/functional/test_framework/test_node.py

@@ -363,10 +363,15 @@ class TestNode():
                 latest_error = suppress_error(f"JSONRPCException {e.error['code']}", e)
             except OSError as e:
                 error_num = e.errno
-                # Work around issue where socket timeouts don't have errno set.
+                if error_num is None:
-                # https://github.com/python/cpython/issues/109601
+                    # Work around issue where socket timeouts don't have errno set.
-                if error_num is None and isinstance(e, TimeoutError):
+                    # https://github.com/python/cpython/issues/109601
-                    error_num = errno.ETIMEDOUT
+                    if isinstance(e, TimeoutError):
+                        error_num = errno.ETIMEDOUT
+                    # http.client.RemoteDisconnected inherits from this type and
+                    # doesn't specify errno.
+                    elif isinstance(e, ConnectionResetError):
+                        error_num = errno.ECONNRESET
 
                 # Suppress similarly to the above JSONRPCException errors.
                 if error_num not in [