Shorten mxs1585

The test description talks about putting the master into maintenance mode
but it spends most of the time putting slaves into maintenance mode. To
make the test more precise (and fast) the test can be reduced to blocking
the most often used slave and the master. The iteration count can also be
lowered from five to two to get at least two cycles of maintenance mode.

maxscale-system-test/mxs1585.cpp

@@ -50,9 +50,9 @@ int main(int argc, char** argv)
         pthread_create(&a, NULL, query_thr, &test);
     }
 
-    for (int i = 0; i < 5; i++)
+    for (int i = 0; i < 2; i++)
     {
-        for (int x = 1; x <= 4; x++)
+        for (int x = 1; x <= 2; x++)
         {
             test.maxscales->ssh_node_f(0, true, "maxadmin set server server%d maintenance", x);
             sleep(1);