EX-6130 lipe: s_volume_name not NUL terminated

EX-6130 lipe: s_volume_name not NUL terminated

s_volume_name field stores string, but the field may have no
termination NUL if the string size equal the size of the field.
Therefore on some target systems the definition of
struct ext2_super_block s_volume_name in
/usr/include/ext2fs/ext2_fs.h may have
attribute "nonstring". In such case it conflicts with calls
which require NUL terminated string.
The fix replaces NUL-terminated string calls by calls with
limited string size (e.g. strlen() -> strnlen())

Signed-off-by: Alexandre Ioffe <aioffe@ddn.com>
Change-Id: Ieb1921a289328a8f9bfae9bb658c6c74f8ec43b7
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/48829
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>