[enhancement](be-meta) sync rocksdb by default to protect data

If performance of user's disks is low, users can change the config
to false, this way users know what would happen if a kernel panic.

be/src/common/config.cpp

@@ -581,7 +581,7 @@ DEFINE_mInt32(result_buffer_cancelled_interval_time, "300");
 DEFINE_mInt32(priority_queue_remaining_tasks_increased_frequency, "512");
 
 // sync tablet_meta when modifying meta
-DEFINE_mBool(sync_tablet_meta, "false");
+DEFINE_mBool(sync_tablet_meta, "true");
 
 // default thrift rpc timeout ms
 DEFINE_mInt32(thrift_rpc_timeout_ms, "60000");