Mu4e: Confirm that lockfile pid is an emacs proc

Or else another app can be given the same PID and we'll be complaining
another Emacs process is using mu4e when that simply isn't true.

modules/email/mu4e/autoload/mu-lock.el

@@ -20,7 +20,8 @@
                    (insert-file-contents +mu4e-lock-file)
                    (buffer-string))))
            (process (process-attributes pid)))
-      (if process (cons pid process)
+      (if (and process (string-match-p "emacs" (alist-get 'args process)))
+          (cons pid process)
         (delete-file +mu4e-lock-file) nil))))
 
 (defun +mu4e-lock-available (&optional strict)