Added check for SVN WebDAV auth request

When repo is SVN and is handled over WebDAV, the authorization error code is `E170001`, but the error message can be other than "authorization failed" if Subversion is installed in another language.
http://subversion.apache.org/docs/api/latest/group__svn__dav__error.html#gada0137a4ffc40251d2fce8ba06ca2e14, http://svn.apache.org/repos/asf/subversion/trunk/subversion/bindings/javahl/src/org/tigris/subversion/javahl/ErrorCodes.java.