Tab-indent continuation lines in the "scan:" section of "zpool status".

All other sections use a tab, which makes them easy to parse. Only the
"scan:" section had its continuation lines indented with four spaces.
This makes them consistent with the others.

Signed-off-by: Remy Blank <remy.blank@pobox.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Closes #3769