Fix flaky test: `Database: test_ns already exists`.

[turboFei]

2025-11-29T08:00:54.3432635Z [INFO] Results:
2025-11-29T08:00:54.3433304Z [INFO] 
2025-11-29T08:00:54.3433738Z [ERROR] Failures: 
2025-11-29T08:00:54.3434507Z [ERROR]   TestInternalMixedCatalogService$TestDatabaseOperation.test:168 expected: <true> but was: <false>
2025-11-29T08:00:54.3435377Z [ERROR] Errors: 
2025-11-29T08:00:54.3437400Z [ERROR]   TestInternalMixedCatalogService$CompatibilityCatalogTests.assertHistoricalCatalogCannotLoadNewTable:376 » ServiceFailure Server error: PersistenceException: org.apache.ibatis.exceptions.PersistenceException: 
2025-11-29T08:00:54.3441306Z ### Error updating database.  Cause: org.apache.derby.shared.common.error.DerbySQLIntegrityConstraintViolationException: The statement was aborted because it would have caused a duplicate key value in a unique or primary key constraint or unique index identified by 'SQL251129080039620' defined on 'TABLE_RUNTIME'.
2025-11-29T08:00:54.3443723Z ### The error may exist in org/apache/amoro/server/persistence/mapper/TableRuntimeMapper.java (best guess)
2025-11-29T08:00:54.3444991Z ### The error may involve org.apache.amoro.server.persistence.mapper.TableRuntimeMapper.insertRuntime-Inline
2025-11-29T08:00:54.3445920Z ### The error occurred while setting parameters
2025-11-29T08:00:54.3446798Z ### SQL: INSERT INTO table_runtime (table_id, group_name, status_code, table_config, table_summary, bucket_id) VALUES (?, ?, ?, ?, ?, ?)
2025-11-29T08:00:54.3449544Z ### Cause: org.apache.derby.shared.common.error.DerbySQLIntegrityConstraintViolationException: The statement was aborted because it would have caused a duplicate key value in a unique or primary key constraint or unique index identified by 'SQL251129080039620' defined on 'TABLE_RUNTIME'.
2025-11-29T08:00:54.3452147Z [ERROR]   TestInternalMixedCatalogService$CompatibilityCatalogTests.setupTest:310 » AlreadyExists Database already exists, test_ns
2025-11-29T08:00:54.3453351Z [ERROR]   TestInternalMixedCatalogService$CompatibilityCatalogTests.setupTest:310 » AlreadyExists Database already exists, test_ns
2025-11-29T08:00:54.3454233Z [ERROR]   TestInternalMixedCatalogService$TestTableCommit.before:247 » AlreadyExists Database: test_ns already exists.
2025-11-29T08:00:54.3455215Z [ERROR]   TestInternalMixedCatalogService$TestTableCommit.before:247 » AlreadyExists Database: test_ns already exists.
2025-11-29T08:00:54.3456044Z [ERROR]   TestInternalMixedCatalogService$TestTableOperation.before:186 » AlreadyExists Database: test_ns already exists.
2025-11-29T08:00:54.3456888Z [ERROR]   TestInternalMixedCatalogService$TestTableOperation.before:186 » AlreadyExists Database: test_ns already exists.