Revert "make excluded threadunsafe tests threadsafe"

This reverts commit 17441cc.

Author: IanButterworth

test/distributed_exec.jl

@@ -159,6 +159,18 @@ function _getenv_include_thread_unsafe()
     return b
 end
 const _env_include_thread_unsafe = _getenv_include_thread_unsafe()
+function include_thread_unsafe_tests()
+    if Threads.maxthreadid() > 1
+        if _env_include_thread_unsafe
+            return true
+        end
+        msg = "Skipping a thread-unsafe test because `Threads.maxthreadid() > 1`"
+        @warn msg Threads.maxthreadid()
+        Test.@test_broken false
+        return false
+    end
+    return true
+end
 
 # Distributed GC tests for Futures
 function test_futures_dgc(id)
@@ -282,14 +294,16 @@ let wid1 = workers()[1],
     fstore = RemoteChannel(wid2)
 
     put!(fstore, rr)
-    # timedwait() is necessary because wid1 is asynchronously informed of
-    # the existence of rr/rrid through the call to `put!(fstore, rr)`.
-    @test timedwait(() -> remotecall_fetch(k -> haskey(Distributed.PGRP.refs, k), wid1, rrid), 10) === :ok
-
+    if include_thread_unsafe_tests()
+        # timedwait() is necessary because wid1 is asynchronously informed of
+        # the existence of rr/rrid through the call to `put!(fstore, rr)`.
+        @test timedwait(() -> remotecall_fetch(k -> haskey(Distributed.PGRP.refs, k), wid1, rrid), 10) === :ok
+    end
     finalize(rr) # finalize locally
     yield() # flush gc msgs
-    @test timedwait(() -> remotecall_fetch(k -> haskey(Distributed.PGRP.refs, k), wid1, rrid), 10) === :ok
-
+    if include_thread_unsafe_tests()
+        @test remotecall_fetch(k -> haskey(Distributed.PGRP.refs, k), wid1, rrid) == true
+    end
     remotecall_fetch(r -> (finalize(take!(r)); yield(); nothing), wid2, fstore) # finalize remotely
     sleep(0.5) # to ensure that wid2 messages have been executed on wid1
     @test poll_while(() -> remotecall_fetch(k -> haskey(Distributed.PGRP.refs, k), wid1, rrid))