Neutron: Clean up documentation typo
Neutron: Clean up documentation typo

Remove duplicate SERVICE_HOST and MYSQL_HOST settings in the
examples.

Change-Id: I0e102b671f03ccb183d30ec6a762d00ebcf1e4b5

richliu/devstack,noironetworks/devstack,bswartz/devstack,samgoon/devstack,dtroyer/devstack,mssumanth/devstack,dirkmueller/devstack,samgoon/devstack,avvocatodemarchis/devstack,thomasem/devstack,bigswitch/devstack,thomasem/devstack,dtroyer/devstack,Mahito/devstack,group-policy/devstack,dirkmueller/devstack,openstack-dev/devstack,varunarya10/devstack,nawawi/openstack,nawawi/openstack,mssumanth/devstack,openstack-dev/devstack,group-policy/devstack,avvocatodemarchis/devstack,bigswitch/devstack,Mahito/devstack,bswartz/devstack,noironetworks/devstack,varunarya10/devstack,richliu/devstack