During migration cleanup, there's a small window in which the storage
group was stopped but not yet removed from the list. So concurrent
operations traversing the list could work with stopped groups.
During a test which emitted schema changes during migrations,
a failure happened when updating the compaction strategy of a table,
but since the group was stopped, the compaction manager was unable
to find the state for that group.
In order to fix it, we'll skip stopped groups when traversing the
list since they're unused at this stage of migration and going away
soon.
Fixes#20699.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Closesscylladb/scylladb#20798
cf58674029