Do not assign publishers when pool assignments are unknown

[gammazero]

If an indexer is offline when the assigner service starts, the assigner cannot read the existing assignments or preferences from that indexer. The assigner will not know what publishers are assigned to that indexer, resulting in assigning those publishers to other indexers as announcements from them arrive. That can result in over-assigning publishers to the indexer pool.

This is further complicated by the assigner not reading preferred assignments (peers that an indexer has previously stored content for but are not assigned to it) when the indexer comes back online. When another indexer has those same preferences, all the assignments are given to the indexer whose preferences are know, even though both indexers are now online.

This is particularly problematic when indexers are newly configured to use an assigner, because most of the assignments happen in a short amount of time as new announce messages arrive. This is what happened on the prod indexers.

To fix this, two things are needed:

• Reset the assignments on the indexers
• Update the assigner to not assign publishers when pool assignments are unknown.