Avoid recruiting extraneous storage server if the down remote data center comes back up

When the remote data center that was down for some time comes back up, DD can recruit new storage servers on processes with class types other than storage. These new storage servers will be marked undesirable as soon as the original storage servers boots up. This extraneous recruitment should be avoided.

Trace the data distributor's storage-server recruitment handling when a remote data center rejoins after an outage. Reproduce the recovery scenario and verify that processes with non-storage class types do not recruit temporary storage servers that become undesirable once the original servers return.

Written by the indexing model from the issue text.