Follow-up to r1437354: Add test for svn_repos_delete().

* subversion/tests/libsvn_repos/repos-test.c
  (test_delete_repos): New test for svn_repos_delete().
  (test_funcs): Add new test to list.
   
Suggested by: philip


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1437414 13f79535-47bb-0310-9956-ffa450edef68