Issue #2624914 by Lars Toomre: Fixes to migrate/src/Tests/*.php files

core/modules/migrate/src/Tests/MigrateDumpAlterInterface.php

core/modules/migrate/src/Tests/MigrateEventsTest.php

core/modules/migrate/src/Tests/MigrateInterruptionTest.php

core/modules/migrate/src/Tests/MigrateMessageTest.php

core/modules/migrate/src/Tests/MigrateRollbackTest.php

core/modules/migrate/src/Tests/MigrateSkipRowTest.php

core/modules/migrate/src/Tests/MigrateStatusTest.php

core/modules/migrate/src/Tests/MigrateTestBase.php

core/modules/migrate/src/Tests/MigrationTest.php

core/modules/migrate/src/Tests/SqlBaseTest.php

core/modules/migrate/src/Tests/TemplateTest.php