LU-16568 lfs: call Parser_exit() at lfs/lctl exit

LU-16568 lfs: call Parser_exit() at lfs/lctl exit

Call Parser_exit() before lfs and lctl cleanly exit
to free memory allocated in Parser_init() via strdup().

Test-Parameters: trivial fstype=zfs testlist=sanity
Signed-off-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Change-Id: I1bc86d4b17f62a545e51fb3e479b2576e6362c42
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/50039
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: jsimmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>