LU-8191 llverfs: fix non-static functions

LU-8191 llverfs: fix non-static functions

Static analysis shows that a number of functions
could be made static. This patch declares several
functions in llverfs.c static.

Making functions new_file() and new_dir() static
causes new format truncation errors. Check the
return of snprintf() to silence these.

Lustre-change: https://review.whamcloud.com/53754
Lustre-commit: 986219131215e44a98703a6fb29d941b5f181aa3

Test-Parameters: trivial
Signed-off-by: Timothy Day <timday@amazon.com>
Change-Id: Ieccf1e40c1da627571a7a95adbb85599185f1342
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/54628
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>