Neutron L3 subnetpool creation should be optional

Added an option to make subnetpools to be optional
as it ignores the public network specified in
FIXED_RANGE.

DocImpact
Change-Id: Ic89ceca76afda67da5545111972c3348011f294f
Closes-Bug: #1628267
diff --git a/doc/source/guides/neutron.rst b/doc/source/guides/neutron.rst
index b26fd1e..78150f3 100644
--- a/doc/source/guides/neutron.rst
+++ b/doc/source/guides/neutron.rst
@@ -392,6 +392,7 @@
         PROVIDER_SUBNET_NAME="provider_net"
         PROVIDER_NETWORK_TYPE="vlan"
         SEGMENTATION_ID=2010
+        USE_SUBNETPOOL=False
 
 In this configuration we are defining FIXED_RANGE to be a
 publicly routed IPv4 subnet. In this specific instance we are using
@@ -577,6 +578,7 @@
     PROVIDER_SUBNET_NAME="provider_net"
     PROVIDER_NETWORK_TYPE="vlan"
     SEGMENTATION_ID=2010
+    USE_SUBNETPOOL=False
 
     [[post-config|/$Q_PLUGIN_CONF_FILE]]
     [macvtap]