message: doc: clarify --concurrency 0
  Risk Level: n/a
  Testing: n/a
  Docs Changes: Clarify doc that concurrency 0 and 1 are equivalent.
  Release Notes: n/a
diff: @@ -69,7 +69,8 @@ following are the command line options that Envoy supports.
  .. option:: --concurrency <integer>
  *(optional)* The number of :ref:`worker threads <arch_overview_threading>` to run. If not
  - specified defaults to the number of hardware threads on the machine.
  + specified defaults to the number of hardware threads on the machine. If set to zero, Envoy will
  + still run one worker thread.
  .. option:: -l <string>, --log-level <string>
  