crash on disk_storage_test unit test

[kostasrim]

See: https://github.com/dragonflydb/dragonfly/actions/runs/8882047978/job/24385805613?pr=2970#step:10:8489

2024-04-29T16:35:59.1018595Z 45: F20240429 16:35:59.101008 23732 external_alloc.cc:366] Check failed: segments_[idx] 
2024-04-29T16:35:59.1021346Z 45: *** Check failure stack trace: ***
2024-04-29T16:35:59.1039700Z 45:     @     0x5591a506d7a5  google::LogMessage::Fail()
2024-04-29T16:35:59.1056305Z 45:     @     0x5591a506d6ec  google::LogMessage::SendToLog()
2024-04-29T16:35:59.1073543Z 45:     @     0x5591a506cee1  google::LogMessage::Flush()
2024-04-29T16:35:59.1091290Z 45:     @     0x5591a5070bf8  google::LogMessageFatal::~LogMessageFatal()
2024-04-29T16:35:59.1116815Z 45:     @     0x5591a4878eec  dfly::tiering::ExternalAllocator::Free()
2024-04-29T16:35:59.1161751Z 45:     @     0x5591a485ba24  dfly::tiering::DiskStorage::MarkAsFree()
2024-04-29T16:35:59.1179668Z 45:     @     0x5591a485f0fd  dfly::tiering::OpManager::ProcessStashed()