add a basic test

Author: IanButterworth

test/distributed_exec.jl

@@ -743,6 +743,7 @@ status = timedwait(() -> isready(f), 10)
 # CachingPool tests
 wp = CachingPool(workers())
 @test [1:100...] == pmap(x->x, wp, 1:100)
+@test fetch(remotecall(myid, wp)) in wp.workers
 
 clear!(wp)
 @test length(wp.map_obj2ref) == 0