Github user jtstorck commented on the issue:
https://github.com/apache/nifi/pull/2482
@mcgilman @scottyaslan I was able to reproduce the bug in master while
proxying with Knox by creating a HandleHttpRequest processor with a
StandardHttpContextMap controller service. Attempting to enable the service
through the UI resulted in the 404. After applying the PR to master and
restarting, I was able to go through the same steps and successfully enable the
StandardHttpContextMap controller service.
+1 LGTM!
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