Replace a timeout task with timedwait()

This should fix an exception seen in CI from the lingering timeout task:
```
 Test Summary:                                | Pass  Total  Time
Deserialization error recovery and include() |   11     11  3.9s
      From worker 4:	Unhandled Task ERROR: EOFError: read end of file
      From worker 4:	Stacktrace:
      From worker 4:	 [1] wait
      From worker 4:	   @ .\asyncevent.jl:159 [inlined]
      From worker 4:	 [2] sleep(sec::Float64)
      From worker 4:	   @ Base .\asyncevent.jl:265
      From worker 4:	 [3] (::DistributedNext.var"#34#37"{DistributedNext.Worker, Float64})()
      From worker 4:	   @ DistributedNext D:\a\DistributedNext.jl\DistributedNext.jl\src\cluster.jl:213
```

Author: JamesWrigley

src/cluster.jl

@@ -194,16 +194,10 @@ function wait_for_conn(w)
         timeout =  worker_timeout() - (time() - w.ct_time)
         timeout <= 0 && error("peer $(w.id) has not connected to $(myid())")
 
-        T = Threads.@spawn Threads.threadpool() begin
-            sleep($timeout)
-            lock(w.c_state) do
-                notify(w.c_state; all=true)
-            end
-        end
-        errormonitor(T)
-        lock(w.c_state) do
-            wait(w.c_state)
-            w.state === W_CREATED && error("peer $(w.id) didn't connect to $(myid()) within $timeout seconds")
+        if timedwait(() -> (@atomic w.state) === WorkerState_connected, timeout) === :timed_out
+            # Notify any waiters on the state and throw
+            @lock w.c_state notify(w.c_state)
+            error("peer $(w.id) didn't connect to $(myid()) within $timeout seconds")
         end
     end
     nothing