tests: use pattern matching to mask `ECONNREFUSED` messages
The second and third one of these in `test-http-proxy.t` was failing on Windows.
The others were found by grep and by failed tests when output was matched and an
attempt was made to emit the mask pattern.
The first clonebundles failure on Windows emitted:
error fetching bundle: [WinError 10061] $ECONNREFUSED$
We should probably stringify that better to get rid of the "[WinError 10061]"
part.
edition = "2018"
max_width = 79
wrap_comments = true
error_on_line_overflow = true