racket--cmd-disconnect: Always set racket--cmd-connecting-p to nil

I noticed when testing on Windows, that sometimes the connection would
not succeed, and furthermore get stuck in a state where
racket--cmd-connecting-p was left non-nil.

This commit fixed that for me.

Although this might have some bearing on issue #344 and issue #348, I
don't have any reason to think this fixes those.

racket-repl.el

@@ -346,6 +346,7 @@ wait for the connection to be established."
 
 (defun racket--cmd-disconnect ()
   "Disconnect from the Racket command process."
+  (setq racket--cmd-connecting-p nil)
   (when racket--cmd-proc
     ;; Sentinel calls us for "deleted" event, which we ourselves will
     ;; trigger with the `delete-process' below. So set
@@ -354,8 +355,7 @@ wait for the connection to be established."
           (buf  (prog1 racket--cmd-buf  (setq racket--cmd-buf nil))))
       (delete-process proc)
       (kill-buffer buf)
-      (clrhash racket--cmd-nonce->callback)
-      (setq racket--cmd-connecting-p nil))))
+      (clrhash racket--cmd-nonce->callback))))
 
 (defun racket--cmd-process-filter (_proc string)
   (let ((buffer racket--cmd-buf))