Some storage arrays are known to return 'illegal request'
when an rtpg extended header request is made.  T10 says the
array should ignore the bit, and return the non-extended
rtpg as the array doesn't support the request.  Working
around this by retrying the rtpg request without the extended
header bit set when the extended rtpg request results in
illegal request.
Signed-off-by: Rob Evers <revers@redhat.com>
Reviewed-by: Babu Moger <babu.moger@netapp.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>