Backport #19049
Unfortunately #18642 does not work because a `*net.OpError` does not implement
the `Is` interface to make `errors.Is` work correctly - thus leading to the
irritating conclusion that a `*net.OpError` is not a `*net.OpError`.
Here we keep the `errors.Is` because presumably this will be fixed at
some point in the golang main source code but also we add a simply type
cast to also check.
Fix#18629
Signed-off-by: Andrew Thornton <art27@cantab.net>
0fe99cc00c