Intermittent Unit Test - TestDownloadManagerStartupRecoveryCombinations

```
=== RUN TestDownloadManagerStartupRecoveryCombinations
time="2024-02-15T21:03:58Z" level=error msg="Error while recovering pending downloads (retries=0): initial error"
time="2024-02-15T21:03:58Z" level=error msg="Failed to recover pending download sharedstorage_download_blob/4bcbf155-7718-4109-a37a-d55c9c9a96d9: FF00138: Invalid UUID supplied: invalid UUID length: 0"
time="2024-02-15T21:03:58Z" level=info msg="Recovering pending download sharedstorage_download_blob/6b7d1215-5505-4b32-93c6-6828ea63663f"
time="2024-02-15T21:03:58Z" level=info msg="Recovering pending download sharedstorage_download_batch/d9138609-0f18-4e55-8898-f462f6380e04"
time="2024-02-15T21:03:58Z" level=info msg="Download manager completed startup after recovering 2 pending downloads"
time="2024-02-15T21:03:58Z" level=error msg="Download operation sharedstorage_download_blob/6b7d1215-5505-4b32-93c6-6828ea63663f attempt=1/1 failed: pop" downloadworker=dw_000
download_manager_test.go:311: PASS: DownloadData(string,string)
download_manager_test.go:311: PASS: DownloadData(string,string)
download_manager_test.go:312: PASS: GetOperations(string,string,string)
download_manager_test.go:312: PASS: GetOperations(string,string,mock.argumentMatcher)
download_manager_test.go:312: PASS: GetOperations(string,string,mock.argumentMatcher)
download_manager_test.go:313: PASS: SharedStorageBatchDownloaded(string,[]uint8)
download_manager_test.go:314: PASS: RegisterHandler(string,string,[]fftypes.FFEnum)
download_manager_test.go:314: PASS: RunOperation(string,mock.argumentMatcher,string)
download_manager_test.go:314: PASS: RunOperation(string,mock.argumentMatcher,string)
download_manager_test.go:314: FAIL: SubmitOperationUpdate(string)
at: [/home/runner/work/firefly/firefly/internal/shareddownload/download_manager_test.go:299]
download_manager_test.go:314: FAIL: 3 out of 4 expectation(s) were met.
The code you are testing needs to make 1 more call(s).
at: [/home/runner/work/firefly/firefly/internal/shareddownload/download_manager_test.go:314]
--- FAIL: TestDownloadManagerStartupRecoveryCombinations (0.00s)
```

Example failed run: https://github.com/hyperledger/firefly/actions/runs/7922223310/attempts/1?pr=1468
[logs_8965.zip](https://github.com/hyperledger/firefly/files/14315164/logs_8965.zip)