storage_service: Make before_change and on_change log print more informative
storage_service: Make before_change and on_change log print more informative

- Make before_change and on_change print the versioned_value
- Print endpoint address first in handle_state_* and
  on_change and friends.

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