storage_service: Warn lost of data when remove a node
storage_service: Warn lost of data when remove a node

If RF = 1 and one node is down, it is possible that data is lost. Warn
this in the logger.

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