org-capture: Update plist before finalizing

* lisp/org-capture.el (org-capture-finalize): Update
`org-capture-plist' with local-value before finalizing.

We use the global-variable `org-capture-plist' to populate the
local-variable `org-capture-current-plist' on the init of the
`org-capture' buffer.  However, we do not do the opposite (i.e. update
the global-variable with the local-variable) on
`org-capture-finalize'.

This is fine for the majority of `org-capture-finalize', since we’re
using the LOCAL arg of `org-capture-get' to read
`org-capture-current-plist' instead of `org-capture-list', but this
trick does not work for `org-capture-after-finalize', since the hook
is run after the `org-capture-buffer' has been closed.

This causes problem with `:kill-buffer t', and it limits what can be
done with cleanup functions in `org-capture-after-finalize'.

See <https://orgmode.org/list/87h7tv9pkm.fsf@hidden/> for details.

lisp/org-capture.el

@@ -732,6 +732,11 @@ captured item after finalizing."
 
   (run-hooks 'org-capture-prepare-finalize-hook)
 
+  ;; Update `org-capture-plist' with the buffer-local value.  Since
+  ;; captures can be run concurrently, this is to ensure that
+  ;; `org-capture-after-finalize-hook' accesses the proper plist.
+  (setq org-capture-plist org-capture-current-plist)
+
   ;; Did we start the clock in this capture buffer?
   (when (and org-capture-clock-was-started
 	     org-clock-marker