PageUpdaterTest and DerivedPageDataUpdaterTest fail when run in isolation.
The failure was obscured by the fact that they work if run after other tests that used schema overrides, like PreMcrRevisionStoreDBTest.
In response to T202116, Ib3e80eb introduced LoadBalancer::setTempTableOnlyMode() to suppresses the CONN_TRX_AUTOCOMMIT flag for a given domain. This is intended to ensure that integration tests don't use an additional database connection that is lacking the "fake" temporary tables with the "unittest_". Table prefix.
However, for this to work, the database domain passed to setTempTableOnlyMode has to include this table prefix. $lb->getLocalDomain() however does not, since MediaWikiIntegrationTestCase::setupDatabaseWithTestPrefix() sets the prefix on the connection, not the LB.
Get the domain for setTempTableOnlyMode() from $db->getDomainID(), so it includes the freshly set table prefix.