Update devref to make latest devstack work

1. add packages(xinetd,tftpd,tftp) to ubuntu pre-install list, they
   are required by the latest ironic devstack plugin.
2. remove "n-novnc" service disable option, it's included by following
   nova disable options.
3. add some descirption to clarify that core services(Horizon, Nova, Cinder)
   don't must be disabled.
4. remove heat disable option, heat is disabled by default, make the
   options be minimal.
5. add IRONIC_TEMPEST_WHOLE_DISK_IMAGE=False, otherwise the Iroinc tempest
   would be failed, because default ironic agent deploy driver require
   partition image, should keep consistent with tempest.
6. remove IRONIC_VM_EPHEMERAL_DISK=0, it's same with default value.
7. remove network options, it's not neccessary, keep the beginner focus
   on the Nimble related options, and keep the demo local.conf clean and
   simple.

Change-Id: Ie389c50c394d2a52938899fc7d2e75dce6167933

doc/source/dev/dev-quickstart.rst

@@ -38,7 +38,7 @@ well.
 
 - Ubuntu/Debian::
 
-    sudo apt-get install build-essential python-dev libssl-dev python-pip libmysqlclient-dev libxml2-dev libxslt-dev libpq-dev git git-review libffi-dev gettext ipmitool psmisc graphviz libjpeg-dev
+    sudo apt-get install build-essential python-dev libssl-dev python-pip libmysqlclient-dev libxml2-dev libxslt-dev libpq-dev git git-review libffi-dev gettext ipmitool psmisc graphviz libjpeg-dev xinetd tftpd tftp
 
 - Fedora 21/RHEL7/CentOS7::
 
@@ -239,7 +239,14 @@ Switch to the stack user and clone DevStack::
     sudo su - stack
     git clone https://git.openstack.org/openstack-dev/devstack.git devstack
 
-Create devstack/local.conf with minimal settings required to enable Nimble::
+Create devstack/local.conf with minimal settings required to enable Nimble
+
+.. note::
+    It's ok to enable Horizon, Nova and Cinder services, they don't impact
+    Nimble at all, disable them in the demo configuration to only deploy the
+    dependent services
+
+::
 
     cd devstack
     cat >local.conf <<END
@@ -261,7 +268,6 @@ Create devstack/local.conf with minimal settings required to enable Nimble::
 
     # Enable Neutron which is required by Ironic and disable nova-network.
     disable_service n-net
-    disable_service n-novnc
     enable_service q-svc
     enable_service q-agt
     enable_service q-dhcp
@@ -275,15 +281,10 @@ Create devstack/local.conf with minimal settings required to enable Nimble::
     enable_service s-container
     enable_service s-account
 
+    # Disable Horizon
+    disable_service Horizon
     # Disable Nova
     disable_service nova n-api n-cpu n-cond n-sch n-novnc n-cauth
-
-    # Disable Horizon
-    disable_service horizon
-
-    # Disable Heat
-    disable_service heat h-api h-api-cfn h-api-cw h-eng
-
     # Disable Cinder
     disable_service cinder c-sch c-api c-vol
 
@@ -302,24 +303,18 @@ Create devstack/local.conf with minimal settings required to enable Nimble::
     # This driver should be in the enabled list above.
     IRONIC_DEPLOY_DRIVER=agent_ipmitool
 
+    # Using Ironic agent deploy driver by default, so don't use whole disk
+    # image in tempest.
+    IRONIC_TEMPEST_WHOLE_DISK_IMAGE=False
+
     # The parameters below represent the minimum possible values to create
     # functional nodes.
     IRONIC_VM_SPECS_RAM=1280
     IRONIC_VM_SPECS_DISK=10
 
-    # Size of the ephemeral partition in GB. Use 0 for no ephemeral partition.
-    IRONIC_VM_EPHEMERAL_DISK=0
-
     # To build your own IPA ramdisk from source, set this to True
     IRONIC_BUILD_DEPLOY_RAMDISK=False
 
-    # By default, DevStack creates a 10.0.0.0/24 network for instances.
-    # If this overlaps with the hosts network, you may adjust with the
-    # following.
-    NETWORK_GATEWAY=10.1.0.1
-    FIXED_RANGE=10.1.0.0/24
-    FIXED_NETWORK_SIZE=256
-
     # Log all output to files
     LOGFILE=$HOME/devstack.log
     LOGDIR=$HOME/logs