Let OVS to connect to the individual IPs of each ODL node

Close-Bug: 1734047

For ODL clustering, one should explicitly points switches to each
of the ODL instances. The openflowplugin logic will figure out
which controller should be the master, and which should be the
slave.

Kolla currently sets the manager to one of the specific ODL over
ptcp and another one through the VIP. The VIP is probably
forwarding the traffic to that same ODL so from ODL's perspective
it's getting two duplicated connection requests from the same OVS
which will cause re-connection problem.

This PS does:
1) Let OVS to connect to the individual IPs of each ODL node in
a ODL cluster instead of only connect to the representative over
VIP. Devstack is doing the same thing[1]. Further more, there is no
need for HAProxy to be frontend for ODL southbound.

2) Delete the unusd ptcp connection option.

[1] https://review.openstack.org/#/c/249484/



Change-Id: Ib57e6fbb5ce64a48be0506904d3c8397ed6f70d9
Signed-off-by: Zhijiang Hu <hu.zhijiang@zte.com.cn>