LU-17611 utils: fix wrong static declarations

LU-17611 utils: fix wrong static declarations

Revert wrong changes made to zfs mount utils

Fixes: c7e9bdf8d4 ("LU-8191 utils: remove unused, fix non-static functions")
Signed-off-by: Mikhail Pershin <mpershin@whamcloud.com>
Change-Id: I162d349ebadbf93a89abf49bd41465979d561423
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/54293
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Timothy Day <timday@amazon.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>