trx_undo_mem_create_at_db_start(): Relax too strict upgrade checks
that were introduced in
commit e46f76c9 (MDEV-15912).
On commit, pages will typically be set to TRX_UNDO_CACHED state.
Having the type TRX_UNDO_INSERT in such pages is common and
unproblematic; the type would be reset in trx_undo_reuse_cached().

trx_rseg_array_init(): On failure, clean up the rollback segments
that were initialized so far, to avoid an assertion failure later
during shutdown.