storage_proxy: mutate_counter_on_leader_and_replicate: use container to get to shard proxy
storage_proxy: mutate_counter_on_leader_and_replicate: use container to get to shard proxy

Rather than using the global helper, get_local_storage_proxy.

Signed-off-by: Benny Halevy <23c997c90eb8537635e9392d48e7af1bf1b2ca22@scylladb.com>
Message-Id: <20220131151516.3461049-2-23c997c90eb8537635e9392d48e7af1bf1b2ca22@scylladb.com>

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