commitlog: Fix use-after-free
commitlog: Fix use-after-free

Remove "finally". Just use a then_wrapped. Which it was originally, before
"handle_exception" was introduced to seastar. Oh, the irony...

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