Illumos #3742

Illumos #3742

3742 zfs comments need cleaner, more consistent style
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Eric Schrock <eric.schrock@delphix.com>
Approved by: Christopher Siden <christopher.siden@delphix.com>

References:
  https://www.illumos.org/issues/3742
  illumos/illumos-gate@f7170741490edba9d1d9c697c177c887172bc741

Ported-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #1775

Porting notes:

1. The change to zfs_vfsops.c was dropped because it involves
   zfs_mount_label_policy, which does not exist in the Linux port.