config: Fail to start if ping timers are invalid

This required adding a lot of return values to two previously
'void' functions. I did two rather than just the one that was
needed because it seemed to make sense to do them both together.

Although these functions now return errors, they are probably
still ignored higher up. this really needs a comprehensive audit.

Signed-off-by: Christine Caulfield <ccaulfie@redhat.com>
Reviewed-by: Jan Friesse <jfriesse@redhat.com>