LU-7063 llog: fix leak of lock in llog_ost_destroy()

LU-7063 llog: fix leak of lock in llog_ost_destroy()

Previous fix
http://review.whamcloud.com/#/c/15730/7/lustre/obdclass/llog_osd.c.
introduced the leak of a lock in the case of an error return from
llog_osd_dir_get().  This fixes that error path.

Signed-off-by: Bob Glossman <bob.glossman@intel.com>
Change-Id: I38f709c5805e23322de988065c83e1a8079bded6
Reviewed-on: http://review.whamcloud.com/16471
Tested-by: Jenkins
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>