fips: Check return value from ftell
* src/fips.c (get_file_offset): Check return value of ftell to be able to detect errors.
Cherry-picked master commit of:
3fd3bb31597f80c76a94ea62e42d58d796beabf1
Originally reported by coverity.
- Signed-off-by: Jakub Jelen <jjelen@redhat.com>