Fix issues spotted when running systemtest with gRPC Frontend

The following issues appear when running the test_client system test with the gRPC frontend.

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Waiting for process took 905 seconds
Launching postrun checks: tests/postrun_checks.sh
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Launching ./postrun_checks.sh -n test-client-12541831 -w error_whitelists/test_client.txt
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Logging to: /home/cirunner/builds/t3_6A3YKT/0/cta/CTA/pod_logs/test-client-12541831/postrun_checks.log
Performing postrun checks
Found 4 logged errors in pod cta-frontend-grpc-0 - container cta-frontend
Found 89 logged errors in pod cta-tpsrv01-0 - container cta-taped-0
Summary of logged error messages:
(whitelisted) Count: 24, Message: "Task failed: counting another error for this session"
(whitelisted) Count: 24, Message: "In RecallReportPacker::ReportError::execute(): failing retrieve job after exception."
(whitelisted) Count: 24, Message: "File writing to disk failed"
(whitelisted) Count: 8, Message: "In Scheduler::reportRetrieveJobsBatch(): failed to report."
(whitelisted) Count: 6, Message: "End of recall session with error(s)"
(whitelisted) Count: 3, Message: "In RetrieveMount::releaseDiskSpace(): reservation release request failed, driveName, diskSystem and mountId do not match."
              Count: 1, Message: "WARNING: The requested file is on tape V00102, which is temporarily unavailable (REPACKING). Please retry later."
              Count: 1, Message: "WARNING: The requested file is on tape V00101, which is temporarily unavailable (REPACKING). Please retry later."
              Count: 1, Message: "File is in fail_on_closew_test storage class, which always fails."
              Count: 1, Message: "Archival of 0-length files not allowed."
Summary of other issues:
Found 0 general pod errors.
Found 0 core dumps.
Found 4 logged errors not in the whitelist.

pipeline: https://gitlab.cern.ch/cta/CTA/-/pipelines/12541831