7938 disable LBA weighting on files and SSDs
Reviewed by: Yuri Pankov <yuripv@gmx.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>

*** 57,66 ****
--- 57,71 ----
          vnode_t *vp;
          vattr_t vattr;
          int error;
  
          /*
+          * Rotational optimizations only make sense on block devices
+          */
+         vd->vdev_nonrot = B_TRUE;
+ 
+         /*
           * We must have a pathname, and it must be absolute.
           */
          if (vd->vdev_path == NULL || vd->vdev_path[0] != '/') {
                  vd->vdev_stat.vs_aux = VDEV_AUX_BAD_LABEL;
                  return (SET_ERROR(EINVAL));