LU-17161 build: Avoid fortify_memset in OBD_FREE_PTR

LU-17161 build: Avoid fortify_memset in OBD_FREE_PTR

OBD_FREE_PTR will optionally clear the about to be free()d
memory.

Unfortunately fortify_memset_chk() hits some false positives.

We can use __underlying_memset() if it is defined, to avoid
the fortify_memset_chk.

Test-Parameters: trivial
Signed-off-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Change-Id: Iced53f22b97ed90e0970625c4fcbaa404054c54a
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/52559
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Petros Koutoupis <petros.koutoupis@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>