rmport: fix and speed up the find_expired() function.
find_expired() is used with -F (report on all expired ports using the
format "date category/port: reason") and -a (remove all expired ports).
- only calculate the deprecation reason for -F
- use nested loops instead of nested recursion for traversing all ports. The nested recursion would also stop after finding the first port.
Approved by: maintainer (crees) (implicit, fixit)