Ticket #471 logconv.pl tool removes the access logs contents if "-M" is not correctly used

https://fedorahosted.org/389/ticket/471
Reviewed by: nhosoi (Thanks!)
Branch: 389-ds-base-1.3.0
Fix Description: Do not call new_stats_block() until we verify that it is safe
to call it.  It will wipe out the file.
Platforms tested: RHEL6 x86_64
Flag Day: no
Doc impact: no
(cherry picked from commit 7447050f572fb8865145d020e9eab64032f667be)
(cherry picked from commit cfbda421535451d99d3ee774a49fc099cfb902f0)
(cherry picked from commit 811300f30264a82b6cd9d0e1d7594a066458912c)