Fix sessiond needed checks

- strncmp should compare up to and _include_ the \0 (was off by one).
  Instead of 2 for "-h", it should be 3. Use "sizeof("-h")" instead of
  hardcoding 3.
- strncmp logic was reversed for the --list-options check.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>