storage_proxy: paxos: don't use global storage_proxy
storage_proxy: paxos: don't use global storage_proxy

Rather than calling get_local_storage_proxy(),
use paxos_response_handler::_proxy.

Signed-off-by: Benny Halevy <23c997c90eb8537635e9392d48e7af1bf1b2ca22@scylladb.com>
Message-Id: <20220131151516.3461049-1-23c997c90eb8537635e9392d48e7af1bf1b2ca22@scylladb.com>

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