storage_service: Serialize rebuild
storage_service: Serialize rebuild

Do not hold the api lock while streaming the data since it might take a
long time, so we need to reconcile other operations while we are in the
middle of rebuild.

scylladb/scylla,kjniemi/scylla,avikivity/scylla,raphaelsc/scylla,kjniemi/scylla,avikivity/scylla,duarten/scylla,raphaelsc/scylla,raphaelsc/scylla,duarten/scylla,scylladb/scylla,kjniemi/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla,duarten/scylla