rpc_test: silence depreceted lambda logger warning
rpc_test: silence depreceted lambda logger warning

Signed-off-by: Botond Dénes <a584fa4d75a0a85d721f44fb6e06315a2853b0b6@scylladb.com>
Message-Id: <20200402144958.795218-2-a584fa4d75a0a85d721f44fb6e06315a2853b0b6@scylladb.com>

cloudius-systems/seastar,syuu1228/seastar,avikivity/seastar,cloudius-systems/seastar,dreamsxin/seastar,dreamsxin/seastar,syuu1228/seastar,syuu1228/seastar,scylladb/seastar,scylladb/seastar,cloudius-systems/seastar,avikivity/seastar,dreamsxin/seastar,avikivity/seastar,scylladb/seastar