Fix ldb --try_load_options doesn't use customized Env (#8929)

Summary:
As title. The reason is that after loading customized options, the env is not set back to the correct one. Fix it.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8929

Test Plan: Manually validate in an environment where the command failed.

Reviewed By: riversand963

Differential Revision: D31026931

fbshipit-source-id: c25dc788bf80ed5bf4b24922c442781943bcd65b

tools/ldb_cmd.cc

@@ -722,6 +722,10 @@ void LDBCommand::PrepareOptions() {
     }
   }
 
+  if (options_.env == Env::Default()) {
+    options_.env = config_options_.env;
+  }
+
   OverrideBaseOptions();
   if (exec_state_.IsFailed()) {
     return;