Add new user option to avoid piling on Dired buffers

* doc/emacs/dired.texi (Dired Visiting): Document it.

* lisp/dired.el (dired-kill-when-opening-new-dired-buffer): New
user option (bug#20598).
(dired-up-directory, dired-find-file): Use it.
(dired--find-possibly-alternative-file): New convenience command
to respect the user option.
3 jobs for master in 31 seconds (queued for 5 seconds)
Status Job ID Name Coverage
  Fast
failed #23246
test-fast-inotify

00:00:16

 
  Normal
failed #23247
test-lisp-inotify

00:00:13

failed #23248
test-lisp-net-inotify

00:00:14

 
Name Stage Failure
failed
test-lisp-net-inotify Normal There has been a runner system failure, please try again
Fetching changes with git depth set to 50...
Reinitialized existing Git repository in /builds/emacs/emacs/.git/
From https://emba.gnu.org/emacs/emacs
* [new ref] 5afe27624f7168713611dc9c24043091f8f820b6 -> refs/pipelines/11386
7a803ec..5afe276 master -> origin/master
Checking out 5afe2762 as master...

Skipping Git submodules setup
ERROR: Job failed (system failure): Error response from daemon: Conflict. The container name "/runner-2oEDrUT7-project-1-concurrent-2-build-4" is already in use by container "da1fe579c662349f5b0cbedeaf385ca8567e208eca419e08e6d3defd24c4f2dc". You have to remove (or rename) that container to be able to reuse that name. (executor_docker.go:726:0s)
failed
test-lisp-inotify Normal There has been a runner system failure, please try again
Using docker image sha256:81f5749c9058a7284e6acd8e126f2b882765a17b9ead14422b51cde1a110b85c for docker:19.03.12 ...
Running on runner-2oEDrUT7-project-1-concurrent-1 via emba.gnu.org...
$ git config --global http.proxy $HTTP_PROXY; git config --global https.proxy $HTTPS_PROXY
Fetching changes with git depth set to 50...
Reinitialized existing Git repository in /builds/emacs/emacs/.git/
Checking out 5afe2762 as master...

Skipping Git submodules setup
ERROR: Job failed (system failure): Error response from daemon: Conflict. The container name "/runner-2oEDrUT7-project-1-concurrent-1-build-4" is already in use by container "f46df44a43bee1f61a6ede2eac732a4e06eaa2094659f7ea23718f093d67bcc6". You have to remove (or rename) that container to be able to reuse that name. (executor_docker.go:726:0s)
failed
test-fast-inotify Fast There has been a runner system failure, please try again
Fetching changes with git depth set to 50...
Reinitialized existing Git repository in /builds/emacs/emacs/.git/
From https://emba.gnu.org/emacs/emacs
* [new ref] 5afe27624f7168713611dc9c24043091f8f820b6 -> refs/pipelines/11386
7a803ec..5afe276 master -> origin/master
Checking out 5afe2762 as master...

Skipping Git submodules setup
ERROR: Job failed (system failure): Error response from daemon: Conflict. The container name "/runner-2oEDrUT7-project-1-concurrent-1-build-4" is already in use by container "f46df44a43bee1f61a6ede2eac732a4e06eaa2094659f7ea23718f093d67bcc6". You have to remove (or rename) that container to be able to reuse that name. (executor_docker.go:726:0s)