Remove some test specific apr_io wrappers that duplicate svn_io code.

* subversion/tests/libsvn_subr/translate-test.c
  (create_file): Use standard error handling wrappers.
  (remove_file): Remove function.

  (substitute_and_verify): Use standard delete functions instead of local
    reimplementation.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1619726 13f79535-47bb-0310-9956-ffa450edef68