[BUG] When a call to OpenSearch back-end times out, Dashboards fails with an Access Denied (403)

[dblock]

Describe the bug

Users get a 403 "Authorization Exception" on some operation in OpenSearch Dashboards. However, the back-end is timing out causing a socket hangup.

[2022-06-24T09:56:06,640][ERROR][c.a.c.e.ReusableRequestHandlerListWithThrottling] [a027a2d9842c375dc47abe3f6e77f0e3] Exception flushing output for request-145983615 url=/xyz/_search?timeout=60000ms&ignore_unavailable=true&rest_total_hits_as_int=true&ignore_throttled=true&preference=1655992403037 context = org.eclipse.jetty.server.AsyncContinuation@f042f7a@REDISPATCHED,resumed with exception org.eclipse.jetty.io.EofException

Expected behavior
Server-side timeouts should not translate into 403s.

OpenSearch Version
All versions.

Dashboards Version
All versions.

[bandinib-amzn]

According to this post: https://stackoverflow.com/questions/35063566/org-eclipse-jetty-io-eofexception-early-eof-thrown-while-uploading-large-file, the org.eclipse.jetty.io.EofException during flushing output for request means the response body content was unable to finish flushing to the network as the connection was terminated. And because of connection termination we are seeing socket hang up in kibana.log.