Disable updatedb OSD directory parsing

It has been reported a couple of months ago by Dan van der Ster from
CERN that updatedb was consumming 100% of CPU while parsing system's
directories. Indeed the process was parsing the OSD PG directories that
might contains billions of objects.

Signed-off-by: Sébastien Han <sebastien.han@enovance.com>
Merge pull request #108 from leseb/change-updatedb

Disable updatedb OSD directory parsing