Use RegexListOutput to generate the expected error so that the repository name
is not specified in the expected error list.

* subversion/tests/cmdline/svnadmin_tests.py
  (verify_keep_going): Use RegexListOutput to generate the expected error
  list. The expected error list looks cleaner.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/verify-keep-going@1457766 13f79535-47bb-0310-9956-ffa450edef68