README.md uses nova SimpleScheduler which doesn't exist

[Accela Zhao]

Using devstack stable/kilo to install multi-node cluster. The [Multi-Note Setup](https://github.com/openstack-dev/devstack/tree/stable/kilo#multi-node-setup) guides user to use

```
SCHEDULER=nova.scheduler.simple.SimpleScheduler
```

However, nova.scheduler.simple.SimpleScheduler doesn't actually exist. See [nova schedulers](https://github.com/openstack/nova/tree/stable/kilo/nova/scheduler). Even though this is just an example, it is misleading enough for beginners to put non-existing SimpleScheduler into local.conf. This results in below error in /opt/stack/logs/screen/screen-n-sch.log

```
/usr/local/bin/nova-scheduler --config-file /etc/nova/nova.conf
2015-05-08 00:44:04.648 4677 DEBUG nova.servicegroup.api [-] ServiceGroup driver defined as an instance of db __init__ /opt/stack/nova/nova/servicegroup/api.py:68
2015-05-08 00:44:04.863 4677 INFO nova.openstack.common.periodic_task [-] Skipping periodic task _periodic_update_dns because its interval is negative
2015-05-08 00:44:04.890 4677 CRITICAL nova [-] ImportError: No module named simple
2015-05-08 00:44:04.890 4677 TRACE nova Traceback (most recent call last):
2015-05-08 00:44:04.890 4677 TRACE nova File "/usr/local/bin/nova-scheduler", line 10, in <module>
2015-05-08 00:44:04.890 4677 TRACE nova sys.exit(main())
2015-05-08 00:44:04.890 4677 TRACE nova File "/opt/stack/nova/nova/cmd/scheduler.py", line 44, in main
2015-05-08 00:44:04.890 4677 TRACE nova topic=CONF.scheduler_topic)
2015-05-08 00:44:04.890 4677 TRACE nova File "/opt/stack/nova/nova/service.py", line 277, in create
2015-05-08 00:44:04.890 4677 TRACE nova db_allowed=db_allowed)
2015-05-08 00:44:04.890 4677 TRACE nova File "/opt/stack/nova/nova/service.py", line 148, in __init__
2015-05-08 00:44:04.890 4677 TRACE nova self.manager = manager_class(host=self.host, *args, **kwargs)
2015-05-08 00:44:04.890 4677 TRACE nova File "/opt/stack/nova/nova/scheduler/manager.py", line 63, in __init__
2015-05-08 00:44:04.890 4677 TRACE nova self.driver = importutils.import_object(scheduler_driver)
2015-05-08 00:44:04.890 4677 TRACE nova File "/usr/local/lib/python2.7/dist-packages/oslo_utils/importutils.py", line 38, in import_object
2015-05-08 00:44:04.890 4677 TRACE nova return import_class(import_str)(*args, **kwargs)
2015-05-08 00:44:04.890 4677 TRACE nova File "/usr/local/lib/python2.7/dist-packages/oslo_utils/importutils.py", line 27, in import_class
2015-05-08 00:44:04.890 4677 TRACE nova __import__(mod_str)
2015-05-08 00:44:04.890 4677 TRACE nova ImportError: No module named simple
2015-05-08 00:44:04.890 4677 TRACE nova
n-sch failed to start
```

[Accela Zhao (accelazh)]

I'm using below local.conf

[[local|localrc]]
GIT_BASE=${GIT_BASE:-https://git.openstack.org}

ADMIN_PASSWORD=secrete
DATABASE_PASSWORD=$ADMIN_PASSWORD
RABBIT_PASSWORD=$ADMIN_PASSWORD
SERVICE_PASSWORD=$ADMIN_PASSWORD
SERVICE_TOKEN=secrete
RECLONE=no

FIXED_RANGE=192.168.120.0/24
NETWORK_GATEWAY=192.168.120.1
FLOATING_RANGE=10.13.182.224/27
PUBLIC_NETWORK_GATEWAY=10.13.182.225
HOST_IP=10.13.182.120

# misc
API_RATE_LIMIT=False
LIBS_FROM_GIT=python-openstackclient

# log
DEBUG=True
VERBOSE=True
DEST=/opt/stack
LOGFILE=$DEST/logs/stack.sh.log
SCREEN_LOGDIR=$DEST/logs/screen

SYSLOG=False
LOG_COLOR=False
LOGDAYS=7

# enable pre-requisites
enable_service rabbit
enable_service mysql
enable_service key

# keystone
KEYSTONE_CATALOG_BACKEND=sql

# enable ceph
enable_service ceph
CEPH_LOOPBACK_DISK_SIZE=10G
CEPH_CONF=/etc/ceph/ceph.conf
CEPH_REPLICAS=3
GLANCE_CEPH_USER=glance
GLANCE_CEPH_POOL=glance
CINDER_DRIVER=ceph
CINDER_CEPH_USER=cinder
CINDER_CEPH_POOL=cinder
CINDER_CEPH_UUID=65B06887-B0EA-427F-B8BD-829AC2E18FF6
CINDER_BAK_CEPH_POOL=cinder_bak
CINDER_BAK_CEPH_USER=cind_bak
CINDER_ENABLED_BACKENDS=ceph,lvm
NOVA_CEPH_POOL=nova

# adjust scheduler to balance VMs
SCHEDULER=nova.scheduler.simple.SimpleScheduler

# disable nova compute on controller node
disable_service n-cpu

# enable swift
enable_service s-proxy
SWIFT_HASH=E75834B828A54832B8AF2294FD8F5C5D
SWIFT_REPLICAS=3
SWIFT_DATA_DIR=$DEST/data/swift

# cinder
enable_service cinder
enable_service c-api
enable_service c-vol
enable_service c-sch
enable_service c-bak

VOLUME_GROUP="stack-volumes"
VOLUME_NAME_PREFIX="volume-"
VOLUME_BACKING_FILE_SIZE=10250M

# enable neutron
disable_service n-net
enable_service q-svc
enable_service q-agt
enable_service q-dhcp
enable_service q-l3
enable_service q-meta
enable_service q-fwaas
enable_service q-lbaas
#enable_service q-vpn
enable_service neutron

# VLAN configuration
Q_PLUGIN=ml2
ENABLE_TENANT_VLANS=True

# GRE tunnel configuration
Q_PLUGIN=ml2
ENABLE_TENANT_TUNNELS=True

# VXLAN tunnel configuration
Q_PLUGIN=ml2
Q_ML2_TENANT_NETWORK_TYPE=vxlan

# enable ceilometer
enable_service ceilometer-acentral
enable_service ceilometer-collector
enable_service ceilometer-alarm-singleton
enable_service ceilometer-alarm-notifier
enable_service ceilometer-alarm-evaluator
enable_service ceilometer-api
CEILOMETER_BACKEND=mongodb

# enable heat
enable_service heat
enable_service h-api
enable_service h-api-cfn
enable_service h-api-cw
enable_service h-eng

# enable horizon
enable_service horizon

# enable tempest
enable_service tempest

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/181465

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/181465
Committed: https://git.openstack.org/cgit/openstack-dev/devstack/commit/?id=ad0a518ca92f86a9f1361d717413f8d1d65d2994
Submitter: Jenkins
Branch: master

commit ad0a518ca92f86a9f1361d717413f8d1d65d2994
Author: Accela Zhao <email address hidden>
Date: Fri May 8 23:55:31 2015 +0800

    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