Fix memory leak in db2 policy DB initialization

Fix memory leak in db2 policy DB initialization

osa_adb_init_db() maintains a static linked list mapping filenames to
lock structures.  Entries are never removed from the list; when their
reference counts hit 0, the lockfile is closed but the filename
remains allocated.  However, the filename is allocated each time the
lockfile is re-opened, leaking the old value.  Fix this leak by moving
filename initialization to entry creation.

(cherry picked from commit f53160634dd5de41c12701ade9e59d4b4dcd645b)

ticket: 8432
version_fixed: 1.14.4