bug fix: free handle from shutdown rpc

examples/margo-example-client.c

@@ -170,6 +170,7 @@ int main(int argc, char **argv)
 
     margo_forward(mid, handle, NULL);
 
+    HG_Destroy(handle);
     HG_Addr_free(hg_class, svr_addr);
 
     /* shut down everything */