LU-4554 lfsck: old single-OI MDT always scrubbed

LU-4554 lfsck: old single-OI MDT always scrubbed

Old ldiskfs MDT's that contain a single OI container named "oi.16"
trigger an automatic OI scrub on each restart.  This is because
osd_oi_table_open() gets ENOENT opening "oi.16.0" and consequently
sets bit 0 in scrub_file::sf_oi_bitmap.  This bit indicates the OI
container 0 needs to be recreated, and it triggers a scrub in
osd_fid_lookup() for lookups that fail with ENOENT.  Fix this by
clearing the bit in osd_oi_init() after a successful open of
"oi.16".

Signed-off-by: Ned Bass <bass6@llnl.gov>
Change-Id: Ie69223d3f8289c90de46f9afe0a2de0e0625b0f6