EX-7968 utils: lamigo to accept multi-word args

EX-7968 utils: lamigo to accept multi-word args

so we can put something like the following into the config file:
mirror-cmd=lfs mirror extend -N --stats --stats-interval=1 -W1M

Test-Parameters: trivial testlist=hot-pools

Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Change-Id: Ib01c4b4c76a46ee44189cc6fa763306b059886b3
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/51768
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>