8972 zfs holds: In scripted mode, do not pad columns with spaces

illumos/illumos-gate@e9b7d6e7f7a6477679a35b73eb3934b096b3dd39

https://www.illumos.org/issues/8972:
'zfs holds -H' does not properly output content in scripted mode. It uses a
tab instead of two spaces, but it still pads column widths with spaces when
it should not.

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Dan McDonald <danmcd@joyent.com>
Author: Allan Jude <allanjude@freebsd.org>