block/iscsi: check WRITE SAME support differently depending on MAY_UNMAP The current check is right for MAY_UNMAP=1. For MAY_UNMAP=0, just try and fall back to regular writes as soon as a WRITE SAME command fails. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Peter Lieven <pl@kamp.de> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>