Today I ran the reimage cookbook as part of T346143 and it suggested the following command:
//Services in confctl are not automatically pooled, to restore the previous state you have to run the following commands:// sudo confctl select 'dc=eqiad,cluster=thanos,service=thanos-swift' set/pooled=yes
Although that might repool hosts that were depooled for different reasons other than reimage, the suggested command should select the affected hostname(s) instead