db: token_ring_table: Filter out tablet-based keyspaces

Querying from virtual table system.token_ring fails if there is a
tablet-based table due to attempt to obtain a per-keyspace erm.

Fix by not showing such keyspaces.

db/system_keyspace.cc

@@ -2026,7 +2026,12 @@ public:
         };
 
         auto keyspace_names = boost::copy_range<std::vector<decorated_keyspace_name>>(
-                _db.get_keyspaces() | boost::adaptors::transformed([this] (auto&& e) {
+            _db.get_keyspaces()
+                | boost::adaptors::filtered([] (auto&& e) {
+                      auto&& rs = e.second.get_replication_strategy();
+                      return rs.is_vnode_based();
+                  })
+                | boost::adaptors::transformed([this] (auto&& e) {
                     return decorated_keyspace_name{e.first, make_partition_key(e.first)};
         }));