Improve lock-pid handling in Tramp

Improve lock-pid handling in Tramp

* lisp/net/tramp-cache.el: Remove comment.

* lisp/net/tramp-gvfs.el (tramp-gvfs-maybe-open-connection):
* lisp/net/tramp-rclone.el (tramp-rclone-maybe-open-connection):
* lisp/net/tramp-sshfs.el (tramp-sshfs-maybe-open-connection):
* lisp/net/tramp-sudoedit.el (tramp-sudoedit-maybe-open-connection):
Do not set "lock-pid" connection-property.
(tramp-sudoedit-handle-delete-file): Use "rm -f".

* lisp/net/tramp.el (tramp-test-message): Extend for buffers w/o
remote default-directory.
(tramp-lock-pid): New defvar.
(tramp-get-lock-pid): Reimplement.