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

*** 1660,1670 ****
           * which is typically around 2:1.  We account for this by assigning
           * higher weight to lower metaslabs (multiplier ranging from 2x to 1x).
           * In effect, this means that we'll select the metaslab with the most
           * free bandwidth rather than simply the one with the most free space.
           */
!         if (metaslab_lba_weighting_enabled) {
                  weight = 2 * weight - (msp->ms_id * weight) / vd->vdev_ms_count;
                  ASSERT(weight >= space && weight <= 2 * space);
          }
  
          /*
--- 1660,1670 ----
           * which is typically around 2:1.  We account for this by assigning
           * higher weight to lower metaslabs (multiplier ranging from 2x to 1x).
           * In effect, this means that we'll select the metaslab with the most
           * free bandwidth rather than simply the one with the most free space.
           */
!         if (!vd->vdev_nonrot && metaslab_lba_weighting_enabled) {
                  weight = 2 * weight - (msp->ms_id * weight) / vd->vdev_ms_count;
                  ASSERT(weight >= space && weight <= 2 * space);
          }
  
          /*