CloudBees Replication Parent 2833

Some REST API endpoint usages in an HA controller are unsupported and return a 400 response with a message about the unsupported details, but previously failed to note that the limitation is specific to HA.

Under some circumstances, potentially involving problems deserializing XML files due to missing objects, a NullPointerException could be returned from QueueAdoption.adopt in an HA controller.

When an agent was deleted with Jenkins while the queue lock was held (for example, when completing a node block running on a cloud agent), a synchronous call to Hazelcast was made. If Hazelcast operations were impeded, this could tie up the queue lock for an extended period of time.