Assign lowest priority to `/**` pattern

Update AntPathMatcher Comparator to treat `/**` in the same way as
`null` paths.

Prior to this commit the pattern `/**` would be picked in preference
to patterns with 3 or more PathVariable (e.g. `/matches/{matchId}/
periods/{periodId}/teams/{teamId}/results`).

Issue: SPR-10550
Merge pull request #304 from antonio-marrero/master

# By Antonio Marrero
* pull304:
  Assign lowest priority to `/**` pattern