multipath: Test that some fatal errors which should not be retried, for example a medium error, correctly generate an I/O error and do not get infinitely retried.

steps:
1.# modprobe scsi_debug num_tgts=1 vpd_use_hostno=0 add_host=2 delay=20  max_luns=2 no_lun_0=1 opts=2
2.# multipath -ll | grep -C 5 scsi_debug
3.# dd if=/dev/zero of=/dev/mapper/$mpathdev bs=1024 seek=2330 count=10
4. check if an I/O error generated