tools/scylla-sstable-index: use defer() to close sstables manager

So it is closed when loading the sstable throws an exception too.
Failing to close the manager will mask the real error as the user will
only see the assert failure due to failing to close the manager.

Signed-off-by: Botond Dénes <bdenes@scylladb.com>
Message-Id: <20210429092248.50968-1-bdenes@scylladb.com>

tools/scylla-sstable-index.cc

@@ -23,6 +23,7 @@
 #include <seastar/core/app-template.hh>
 #include <seastar/core/seastar.hh>
 #include <seastar/util/log.hh>
+#include <seastar/util/closeable.hh>
 
 #include "schema_builder.hh"
 #include "db/marshal/type_parser.hh"
@@ -167,6 +168,7 @@ Note: UDT is not supported for now.
             db::config dbcfg;
             gms::feature_service feature_service(gms::feature_config_from_db_config(dbcfg));
             sstables::sstables_manager sst_man(large_data_handler, dbcfg, feature_service);
+            auto close_sst_man = deferred_close(sst_man);
 
             auto ed = sstables::entry_descriptor::make_descriptor(dir_path.c_str(), sst_filename.c_str());
             auto sst = sst_man.make_sstable(primary_key_schema, dir_path.c_str(), ed.generation, ed.version, ed.format);
@@ -182,8 +184,6 @@ Note: UDT is not supported for now.
             }
 
             sst = {};
-
-            sst_man.close().get();
         });
     });
 }