LU-7443 llog: remove unused and empty llog

LU-7443 llog: remove unused and empty llog

This patch adds ability to remove plain llog during record
cancellation for inactive plain llog. Before it such files
were removed during mount operation. And this is not enough
for changelog. The current marker of catalog could reach the
undeleted record, and this causes changelog problem.

Signed-off-by: Alexander Boyko <alexander.boyko@seagate.com>
Seagate-bug-id: MRP-2897
Change-Id: Ic24a1643f2fb264ad1212668e382a0bbc9b735b7
Reviewed-on: http://review.whamcloud.com/17227
Tested-by: Jenkins
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>