alternator: Take token metadata from server's storage_proxy
alternator: Take token metadata from server's storage_proxy

There's a local_nodelist_handler serving API requests that calls
for global storage service to get token metadata from. Now it
can get storage proxy reference from server upon construction
and use it for tokens.

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

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