Allow verification status to be cleared with cta-admin

Introduction

• Related ops issue: https://gitlab.cern.ch/cta/operations/-/issues/857

At the moment it is not possible to remove the verification status from the tape:

[root@ctaproductionfrontend02 bin]# cta-admin --json tape ls -v I40003 | jq . | grep veri
    "verificationStatus": "{\"date\": 1662383510, \"status\": \"ongoing\", \"files_submitted\": 811, \"files_verified\": 0, \"files_failed\": 0}"

[root@ctaproductionfrontend02 bin]# cta-admin tape ch -v I40003 --vs ""
modifyTapeVerificationStatus: bindString failed: paramName=:VERIFICATION_STATUS: bindString failed for SQL statement UPDATE TAPE SET VERIFICATION_STATUS = :VERIFICATION_STATUS,LAST_UPDATE_USER_N...: Optional string parameter :VERIFICATION_STATUS is an empty string.  An optional string parameter should either have a non-empty string value or no value at all.

This is inconsistent with the fact that tapes that have not yet been verified do not have any value there:

[root@ctaproductionfrontend02 bin]# cta-admin --json tape ls -v I40018 | jq . | grep veri
    "verificationStatus": ""

Proposed solution

Allow verification status to be cleared with cta-admin.