bug fix

get_size() is the right function, just keep in mind that it doesn't
count the caller, only work units that are queued for future execution
in the pool

src/margo.c

@@ -119,8 +119,8 @@ static void hg_progress_fn(void* foo)
 
         if(!mid->hg_progress_shutdown_flag)
         {
-            ABT_pool_get_total_size(mid->progress_pool, &size);
-            if(size > 1)
+            ABT_pool_get_size(mid->progress_pool, &size);
+            if(size > 0)
             {
                 HG_Progress(mid->hg_class, mid->hg_context, 0);
                 ABT_thread_yield();