Leak fixes
* kern/disk.c (grub_disk_cache_store): Invalidate previous cache
in case of collision
* disk/scsi.c (grub_scsi_open): free scsi in case of error
* disk/scsi.c (grub_scsi_read10): Use scsi->blocksize instead
of 512 to calculate data size.
(grub_scsi_read12): Likewise.
(grub_scsi_write10): Likewise.
(grub_scsi_write12): Likewise.
(grub_scsi_read): Adjust size according to blocksize.
Add checks for invalid blocksize and unaligned transfer.
* disk/ata.c (grub_apapi_open): Initialize devfnd, no need to set
scsi->name and scsi->luns, as they will be set in grub_scsi_open.
* disk/scsi.c (grub_scsi_open): Don't call p->close (scsi) here when
error occurs, as grub_disk_open will call grub_disk_close, which will
call p->close (scsi).
