Init cooperative wait test for multiple threads

In the cooperative wait test multiple threads are calling MPI functions
in a non-serialized way. Thus, MPI needs to be initialized with
`threadlevel=:multiple`.

Author: lcw

test/test_cooperative_wait.jl

@@ -1,7 +1,7 @@
 # tests for the various kinds of waits
 include("common.jl")
 
-MPI.Init()
+MPI.Init(threadlevel=:multiple)
 
 myrank = MPI.Comm_rank(MPI.COMM_WORLD)
 commsize = MPI.Comm_rank(MPI.COMM_WORLD)