MDEV-31173 : Server crashes when setting wsrep_cluster_address after …

[janlindstrom]

…adding invalid value to wsrep_allowlist table

• [x] The Jira issue number for this PR is: MDEV-31173

Description

Problem was that wsrep_schema tables were not marked as category information. Fix allows access to wsrep_schema tables even when node is detached.

How can this PR be tested?

TODO: modify the automated test suite to verify that the PR causes MariaDB to behave as intended. Consult the documentation on "Writing good test cases".

If the changes are not amenable to automated testing, please explain why not and carefully describe how to test manually.

Basing the PR against the correct MariaDB version

• [ ] This is a new feature and the PR is based against the latest MariaDB development branch.
• [ x] This is a bug fix and the PR is based against the earliest maintained branch in which the bug can be reproduced.

PR quality check

• [ x] I checked the CODING_STANDARDS.md file and my PR conforms to this where appropriate.
• [ x] For any trivial modifications to the PR, I am ok with the reviewer making the changes themselves.