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.

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PROVENANCE: Today I noticed commit 98bb9c7 and commit cedf4ba linked
to from the above issues. But I do not have either commit in any of my
local repos, not even according to `git fsck --lost-found`. WAT.

I suspect what happened was that I made a topic branch and pushed a
commit, which is why GitHub got it (and apparently will keep it
indefinitely because of the link from comments). But then I deleted
the branch without merging. Or possibly that commit was rebased away
before merging the branch.

Probably this happened on a new Windows laptop. In my defense,
mid-January I was moving between Mac and Windows, as part of an effort
to improve racket-mode support on the latter. And then, a Linux laptop
got added to the mix, as well.

In any case I'm going to recover and use this commit, now. The bit
above the horizontal line is the commit message.

Author: Greg Hendershott

racket-repl.el

@@ -362,6 +362,7 @@ 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
@@ -370,8 +371,7 @@ 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))