LU-5451 lod: improve weird FID handling

LU-5451 lod: improve weird FID handling

In lod_fld_lookup() the FID in question may have come from disk or
wire. Thus if fid_is_sane() returns false then return -EIO rather than
asserting.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: I6c7e3885a8b1aa81fcaa8891392a11e40a02fbce
Reviewed-on: http://review.whamcloud.com/11560
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>