Update neutron-vpn-agent path

Fix path of vpn-agent as same as lbaas

- If q-vpn service is enabled, this patch switches the l3-agent to
vpn-agent

Change-Id: Ifbe3d51b5c89f759a71e904960c5f6cc99c44a5f
diff --git a/lib/neutron_plugins/services/vpn b/lib/neutron_plugins/services/vpn
index 3c030c5..0a79a69 100644
--- a/lib/neutron_plugins/services/vpn
+++ b/lib/neutron_plugins/services/vpn
@@ -6,7 +6,7 @@
 set +o xtrace
 
 
-VPN_BINARY="$NEUTRON_DIR/bin/neutron-vpn-agent"
+AGENT_VPN_BINARY="$NEUTRON_BIN_DIR/neutron-vpn-agent"
 VPN_PLUGIN="neutron.services.vpn.plugin.VPNDriverPlugin"
 
 function neutron_vpn_install_agent_packages() {
@@ -21,9 +21,5 @@
     fi
 }
 
-function neutron_vpn_configure_agent() {
-    AGENT_L3_BINARY="$NEUTRON_DIR/bin/neutron-vpn-agent"
-}
-
 # Restore xtrace
 $MY_XTRACE