LU-9153 llog: consolidate common error checking

LU-9153 llog: consolidate common error checking

Consolidate error checking for corrupted and empty llog files
detected when the llog file is being opened into a single
routine llog_cat_process_common().

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: I575343f486e7420c51466f9923b841c37f3ebbe5
Reviewed-on: https://review.whamcloud.com/26211
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Faccini Bruno <bruno.faccini@intel.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>