In specific circumstances, a pool that is in the internal stopped_pools data structure does not appear in D-Bus stopped pools property

[mulkieran]

This circumstance can occur only if stratisd judges some devices in the pool to be encryption-supporting and some not. This situation is fairly unusual. It can be caused by overwriting Stratis LUKS metadata with a key_description that does not appear to belong to Stratis. In that case, the LUKS info that stratisd tracks is discarded and there are some encrypted devices and some not in the DeviceSet. In this case, the device set is omitted from the information that is included in StoppedPools.

One way to address this is to add extra information at the lowest level about the Stratis device that has no useful unlocking information, something like UnknownUnlockMethod. Then, rather than omitting the LUKS info from the internal data structures, we would include it. In that case, we would be able to setup the pool from the unlocked device, but we would also want to put it into a NO_IPC_REQUESTS state to alert the user that there was a problem.

Related #3353