storage_proxy: use logger's exception printer to report read failure
storage_proxy: use logger's exception printer to report read failure

Use existing exception pretty printer since it handles nested
exceptions.

Message-Id: <671d467ddf20f1b51c2805d2150a48309991faca@scylladb.com>

duarten/scylla,duarten/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla,duarten/scylla,avikivity/scylla,scylladb/scylla,avikivity/scylla