EX-9007 lipe: Fix getting client mount path

EX-9007 lipe: Fix getting client mount path

This patch fixes a "Segmentation fault" issue related
to the generation of size statistics report in '*.json'
format when the client is unmounted

Test-Parameters: trivial testlist=sanity-lipe-scan3
Signed-off-by: Vitaliy Kuznetsov <vkuznetsov@ddn.com>
Change-Id: Ibae2fa2428ae7e202b08acae9354f303bbdbd739
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/54284
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Colin Faber <cfaber@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>