REST client not attempting fallback hosts upon httpOpenTimeout expiry

[owenpearson]

It has been observed that when using the generic request method, if ClientOptions.httpOpenTimeout expires, clients do not retry the request with fallback hosts, but instead fail immediately with java.net.SocketTimeoutException: Connect timed out.

This should be easy enough to reproduce by setting httpOpenTimeout sufficiently low and observing in logs whether the client attempts to use fallback hosts.

We should also check whether fallback hosts are attempted for other timeouts, in particular, httpRequestTimeout (nb: until #310 is resolved, the default httpRequestTimeout is the same as httpMaxRetryDuration so probably won't try fallbacks if expired anyway).

┆Issue is synchronized with this Jira Task by Unito