Update the repos tests to use proper path functions instead of apr_pstrcat to
avoid problems like those fixed in r1537364.

* subversion/tests/libsvn_repos/repos-test.c
  (in_repo_authz,
   in_repo_groups_authz,
   test_config_pool): Use proper uri and dirent functions instead of guessing.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1537412 13f79535-47bb-0310-9956-ffa450edef68