On svn-auth-x509 branch, during the auth subcommand treat errors from the X.509
parser as warnings.

* subversion/svn/auth-cmd.c
  (show_cert): Handle errors from svn_x509_parse_cert() as warnings.

Suggested by: ivan


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/svn-auth-x509@1618581 13f79535-47bb-0310-9956-ffa450edef68