Handle early exit in DBErrorHandlingFSTests

Summary: To avoid use-after-free on custom env on ASSERT_WHATEVER
failure.

This is motivated by a rare crash seen in DBErrorHandlingFSTest.WALWriteError
(VersionSet::GetObsoleteFiles in a SstFileManagerImpl::ClearError
thread) and wanting to rule out this being related to that.

Test Plan: manually seeing ASSERT_WHATEVER failures, especially under
ASAN

db/error_handler_fs_test.cc

@@ -30,6 +30,14 @@ class DBErrorHandlingFSTest : public DBTestBase {
     fault_env_.reset(new CompositeEnvWrapper(env_, fault_fs_));
   }
 
+  ~DBErrorHandlingFSTest() {
+    // Before destroying fault_env_
+    SyncPoint::GetInstance()->DisableProcessing();
+    SyncPoint::GetInstance()->LoadDependency({});
+    SyncPoint::GetInstance()->ClearAllCallBacks();
+    Close();
+  }
+
   std::string GetManifestNameFromLiveFiles() {
     std::vector<std::string> live_files;
     uint64_t manifest_size;