bug#51327: 28.0.60; emacsclient warns about XDG_RUNTIME_DIR when starting daemon on-demand

[Ulrich Mueller]

>>>>> On Thu, 09 Dec 2021, Paul Eggert wrote:

>> * Otherwise, revert to the Emacs 27 behavior and come up with a
>> better solution for Emacs 29.

> That sounds better, if the EMACS_SOCKET_NAME approach is good enough.
> Proposed patch attached. This patch attempts to be reasonably minimal
> vs what's in emacs-28 now (as opposed to cleaning up this
> somewhat-messy area).

I could live with this solution for now.