DAOS-16276 doc: Link to suspect ranks (#15508)

Update "engines become unavailable" in admin/troubleshooting.md to link
to the new "suspect ranks" description.

Signed-off-by: Li Wei <[email protected]>

docs/admin/troubleshooting.md

@@ -556,7 +556,7 @@ Alternately, the administrator may erase and re-format the DAOS system to start
 
 ### Engines become unavailable
 
-Engines may become unavailable due to server power losses and reboots, network switch failures, etc. After staying unavailable for a certain period of time, these engines may become "excluded" or "errored" in `dmg system query` output. Once the states of all engines stabilize (see [`CRT_EVENT_DELAY`](env_variables.md)), each pool will check whether there is enough redundancy (see [Pool RF](pool_operations.md#pool-redundancy-factor)) to tolerate the unavailability of the "excluded" or "errored" engines. If there is enough redundancy, these engines will be excluded from the pool ("disabled ranks" in `dmg pool query --health-only` output); otherwise, the pool will perform no exclusion and may become temporarily unavailable (as seen by timeouts of `dmg pool query`, `dmg pool list`, etc.). Similarly, when engines become available, whenever the states of all engines stabilize, each pool will perform the aforementioned check for any unavailable engines that remain.
+Engines may become unavailable due to server power losses and reboots, network switch failures, etc. After staying unavailable for a certain period of time, these engines may become "excluded" or "errored" in `dmg system query` output. Once the states of all engines stabilize (see [`CRT_EVENT_DELAY`](env_variables.md)), each pool will check whether there is enough redundancy (see [Pool RF](pool_operations.md#pool-redundancy-factor)) to tolerate the unavailability of the "excluded" or "errored" engines. If there is enough redundancy, these engines will be excluded from the pool ("disabled ranks" in `dmg pool query --health-only` output); otherwise, the pool will perform no exclusion ("suspect ranks" in `dmg pool query --health-only` output as described in [Querying a Pool](pool_operations.md#querying-a-pool)) and may become temporarily unavailable (as seen by timeouts of `dmg pool query`, `dmg pool list`, etc.). Similarly, when engines become available, whenever the states of all engines stabilize, each pool will perform the aforementioned check for any unavailable engines that remain.
 
 To restore availability as well as capacity and performance, try to start all "excluded" or "errored" engines. Starting all of them at the same time minimizes the chance of triggering rebuild jobs. In many cases, the following command suffices:
 ```