Allow setting --bind-address for apiserver hyperkube (#1985)

* Allow setting --bind-address for apiserver hyperkube

This is required if you wish to configure a loadbalancer (e.g haproxy)
running on the master nodes without choosing a different port for the
vip from that used by the API - in this case you need the API to bind to
a specific interface, then haproxy can bind the same port on the VIP:

root@overcloud-controller-0 ~]# netstat -taupen | grep 6443
tcp        0      0 192.168.24.6:6443       0.0.0.0:*               LISTEN      0          680613     134504/haproxy
tcp        0      0 192.168.24.16:6443      0.0.0.0:*               LISTEN      0          653329     131423/hyperkube
tcp        0      0 192.168.24.16:6443      192.168.24.16:58404     ESTABLISHED 0          652991     131423/hyperkube
tcp        0      0 192.168.24.16:58404     192.168.24.16:6443      ESTABLISHED 0          652986     131423/hyperkube

This can be achieved e.g via:

kube_apiserver_bind_address: 192.168.24.16

* Address code review feedback

* Update kube-apiserver.manifest.j2