Fix verify_master_failure

The log message had changed, changed test to match. Also, the remaining
delay is now printed.

maxscale-system-test/verify_master_failure.cpp

@@ -14,7 +14,7 @@ int main(int argc, char* argv[])
     test.tprintf("Blocking master and checking that master failure is delayed at least once.");
     test.repl->block_node(0);
     sleep(5);
-    test.log_includes(0, "delaying.*failover");
+    test.log_includes(0, "Delaying failover");
 
     test.tprintf("Waiting to see if failover is performed.");
     sleep(10);