It could happen that system_distributed_keyspace was used by
storage_service before it was fully started (inside
`handle_cdc_generation`), i.e. before sys_dist_ks' `start()` returned
(on shard 0). It only checked whether `local_is_initialized()` returns
true, so it only ensured that the service is constructed.
Currently, sys_dist_ks' `start` only announces migrations, so this was
mostly harmless. More concretely: it could result in the node trying to
send CQL requests using a table that it didn't yet recognize by calling
sys_dist_ks' methods before the `announce_migration` call inside `start`
has returned. This would result in an exception; however, the exception
would be catched by the caller and the procedure would be retried,
succeeding eventually. See `handle_cdc_generation` for details.
Still, the initial intention of the code was to wait for the sys_dist_ks
service to be fully started before it was used. This commit fixes that.
0df15ca8cc