sbin/hammer: Make strtrl() api right [2/3]
- Fix changes made by commit
3c10747d.
- Not sure what the return value of strtrl() is trying to do, but
checking ==NULL here doesn't mean anything unless 'path' is NULL.
(The only case that had meaning was when 'path' was NULL, but
it's pretty obvious callers were not passing NULL)
- Change strnlen() to strlen(). It's better to use strlen() when
we know the input (argv[i]) is a C string. Also note that in
this case non NULL terminated char[] of length 'size_t maxlen'
is useless and does no good anyway.