LU-12137 osd-ldiskfs: implement proper error handling in osd_ios_OBJECTS_scan

LU-12137 osd-ldiskfs: implement proper error handling in osd_ios_OBJECTS_scan

In the linux kernel it is considered proper coding style to
handle error codes returned by functions instead of successful
completions. Reverse the error handling of the return values from
osd_ios_lookup_one_len(). This also reduces the code indentation
and makes it easier to follow.

Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Change-Id: Idd3b91218f80a88d69206d3c2570bea22ff1fbb1
Reviewed-on: https://review.whamcloud.com/35644
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Neil Brown <neilb@suse.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Yang Sheng <ys@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>