transport/controller: Rework try-catch into defers
transport/controller: Rework try-catch into defers

This is to make further patching simpler.

Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla