Allow credentials cleanup even when the 'no-auth-cache' option is set.
If someone doesn't want to fiddle with their auth cache, they
shouldn't call this function.  Also, don't send credentials through
the cleanup callback which are not ultimately managed by Subversion
(because they live in a third-party security provider).

* subversion/libsvn_subr/simple_providers.c
  (svn_auth__simple_cleanup_walk): Allow cleanup even when
    'no-auth-cache' flag is set.  Don't allow cleanup of credentials
    which are housed in third-party providers.  Finally, stop passing
    a cred kind value as a provider.  Strictly speaking, we don't even
    have a name for our proprietary Subversion caching provider, but
    there's at least some degree of precedent for using the "simple"
    password type string, so run with that for now.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1465112 13f79535-47bb-0310-9956-ffa450edef68