NIFI-8321 Add NoRouteToHostException

[yapjiahong]

Description of PR

• Although the HttpClient has thrown an "IOException" and the "StandardRemoteGroupPort", has caught the "IOException"

• but the HttpClient never throw "NoRouteToHostException",

• therefore, "StandardRemoteGroupPort" will never catch the exception and still try to create lots of HTTP connections when "NoRouteToHostException" happens

• "NoRouteToHostException" => when a host/instance suddenly shutdown or remove..., but the RemoteProcessGroup still enable or working.

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[github-actions]

We're marking this PR as stale due to lack of updates in the past few months. If after another couple of weeks the stale label has not been removed this PR will be closed. This stale marker and eventual auto close does not indicate a judgement of the PR just lack of reviewer bandwidth and helps us keep the PR queue more manageable. If you would like this PR re-opened you can do so and a committer can remove the stale tag. Or you can open a new PR. Try to help review other PRs to increase PR review bandwidth which in turn helps yours.