scanner: Close input resource when done to prevent leak

Addresses this error reported by Denis Denisov:

  [src/scanner.c:1415]: (error) Resource leak: input

Signed-off-by: Bryce Harrington <bryce@osg.samsung.com>

v2: Also close input for other exit points in main.
Signed-off-by: Bryce Harrington <bryce@osg.samsung.com>
Reviewed-by: Jonas Ådahl <jadahl@gmail.com>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: David FORT <contact@hardening-consulting.com>