Use an actual existing nova scheduler in README.md

The Multi-Node Setup guide in README.md

    https://github.com/openstack-dev/devstack/tree/master#multi-node-setup

guides users to use

    SCHEDULER=nova.scheduler.simple.SimpleScheduler

where the SimpleScheduler doesn't actually exist in nova. Even
though this is just an example, it is misleading enough for a
beginner to put SimpleScheduler into local.conf. The resulting
error message where n-sch fails to start

    ImportError: No module named simple

Isn't intuitive enough and may takes the beginner long time to
locate what's wrong.

This patch replaces SimpleScheduler with a real existing
FilterScheduler in nova.

Change-Id: I14a2a5c0604ce08a498accfc3a795c1c9aa3e642
Closes-bug: #1453186
diff --git a/README.md b/README.md
index 04f5fd9..7ba4e74 100644
--- a/README.md
+++ b/README.md
@@ -328,7 +328,7 @@
 You likely want to change your `localrc` section to run a scheduler that
 will balance VMs across hosts:
 
-    SCHEDULER=nova.scheduler.simple.SimpleScheduler
+    SCHEDULER=nova.scheduler.filter_scheduler.FilterScheduler
 
 You can then run many compute nodes, each of which should have a `stackrc`
 which includes the following, with the IP address of the above controller node: