Update doc to reflect neutron became devstack default

Removing the explicit enablment of Neutron services, as with [1] they are configured as defaults in stackrc.

[1] https://review.openstack.org/#/c/350750/

Change-Id: Ic8910cd28fe37842f7d824e68bd2ea705e7e52de
diff --git a/doc/source/guides/neutron.rst b/doc/source/guides/neutron.rst
index c5b1634..b26fd1e 100644
--- a/doc/source/guides/neutron.rst
+++ b/doc/source/guides/neutron.rst
@@ -76,12 +76,6 @@
         RABBIT_PASSWORD=secret
         SERVICE_PASSWORD=secret
 
-        # Do not use Nova-Network
-        disable_service n-net
-        # Enable Neutron
-        ENABLED_SERVICES+=,q-svc,q-dhcp,q-meta,q-agt,q-l3
-
-
         ## Neutron options
         Q_USE_SECGROUP=True
         FLOATING_RANGE="172.18.161.0/24"
@@ -389,11 +383,7 @@
 
         Q_USE_PROVIDER_NETWORKING=True
 
-        # Do not use Nova-Network
-        disable_service n-net
-
-        # Neutron
-        ENABLED_SERVICES+=,q-svc,q-dhcp,q-meta,q-agt
+        disable_service q-l3
 
         ## Neutron Networking options used to create Neutron Subnets
 
@@ -530,12 +520,6 @@
     RABBIT_PASSWORD=secret
     SERVICE_PASSWORD=secret
 
-    # Do not use Nova-Network
-    disable_service n-net
-    # Enable Neutron
-    ENABLED_SERVICES+=,q-svc,q-dhcp,q-meta,q-agt,q-l3
-
-
     ## Neutron options
     Q_USE_SECGROUP=True
     FLOATING_RANGE="172.18.161.0/24"
@@ -582,10 +566,7 @@
     Q_ML2_PLUGIN_MECHANISM_DRIVERS=macvtap
     Q_USE_PROVIDER_NETWORKING=True
 
-    #Enable Neutron services
-    disable_service n-net
     enable_plugin neutron git://git.openstack.org/openstack/neutron
-    ENABLED_SERVICES+=,q-agt,q-svc
 
     ## MacVTap agent options
     Q_AGENT=macvtap