Avoid overwrite value of deprecated name in conf.
Avoid overwrite value of deprecated name in conf.

See bug/1194064 #2 Mark McLoughlin's comment

Fixes: Bug #1194064

Change-Id: I421d2decfa8829796fe7b6c14f954f3cccc17215

gotostack/neutron-lbaas,gandelman-a/neutron-lbaas,gotostack/neutron-lbaas,gandelman-a/neutron-lbaas,dougwig/x-neutron-lbaas,citrix-openstack-build/neutron-lbaas,gandelman-a/neutron-lbaas,gotostack/neutron-lbaas