storage_service: Wait for seastar::get_units in node_ops
storage_service: Wait for seastar::get_units in node_ops

The seastar::get_units returns a future, we have to wait for it.

Fixes #9767

Closes #9768

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