DVR lost centralized floating ip when the ha state switched.

[sunzuohua]

Reproduction steps:
The l3 agent mode is as follows:
    Network:dvr_snat
    Compute:dvr_no_external
1、Create a DVR(HA). Then add interface and gateway to the DVR.
2、Create a vm and associate a floating ip to the vm.
3、Check the keepalived.conf and snat ns on the master and backup network nodes for the DVR.
4、The floating ip can be found in the keepalived.conf on the master network node but not in the keepalived.conf on the backup network node for the DVR .On the master network node for the DVR , the floating ip is found normal in the snat ns.
5.Swith the ha state of the DVR, Check the keepalived.conf and snat ns on the current master network node for the DVR.
6.The floating ip still can not be found in the keepalived.conf on the current master network node. And on the current master network node for the DVR , the floating ip is not found in the snat ns.

Mybe the check for the router ha state[1] should be moved just before [2].

[1]https://github.com/openstack/neutron/blob/master/neutron/agent/l3/dvr_edge_ha_router.py#L61
[2]https://github.com/openstack/neutron/blob/master/neutron/agent/l3/dvr_edge_ha_router.py#L65