Client refactor: Remove usage of Lwt_unix from Lwt_dropbox

src/lib_shell/worker.ml

@@ -196,7 +196,8 @@ module Make
             Lwt_dropbox.take message_box >>= fun m ->
             return (Some m)
         | Some timeout ->
-            Lwt_dropbox.take_with_timeout timeout message_box >>= fun m ->
+            Lwt_dropbox.take_with_timeout
+              (Lwt_unix.sleep timeout) message_box >>= fun m ->
             return m
 
   let trigger_shutdown w =

src/lib_stdlib_lwt/lwt_dropbox.ml

@@ -88,6 +88,3 @@ let rec take_with_timeout timeout dropbox =
           take_with_timeout timeout dropbox
       else
         Lwt.return_none
-
-let take_with_timeout timeout dropbox =
-  take_with_timeout (Lwt_unix.sleep timeout) dropbox

src/lib_stdlib_lwt/lwt_dropbox.mli

@@ -26,7 +26,7 @@ val take: 'a t -> 'a Lwt.t
     The elements is removed from the dropbox. The function might return
     [Closed] if the dropbox is empty and closed. *)
 
-val take_with_timeout: float -> 'a t -> 'a option Lwt.t
+val take_with_timeout: unit Lwt.t -> 'a t -> 'a option Lwt.t
 (** Like [take] except that it returns [None] after [timeout seconds]
     if the dropbox is still empty. *)