lsvfs: restyle, no functional change

Namely:

• main was using two-space indentation
• re-sort local variables
• explicit braces for loop scope
• make flag bit comparison explicit

The first line of this commit message is unfortunately a lie, as it
introduces a minor functional change on non-FreeBSD systems. Namely,
the first branch is now explicitly compared against 0 and the choice
was made to compare it as greater than 0 to avoid issues on other
systems where argc != 0 on entry isn't guaranteed (negative when
checked there).

Sponsored by: Klara, Inc.