use openstack command instead of nova command
use openstack command instead of nova command

In function 'get_instance_ip', 'nova' client command is used to get
instance information in order to retrive IP address of the instance.

There is no need to use the nova command, since 'openstack' client
already supports such basic operation.

Moreover, 'openstack' client has an option to get value of specified
column. That brings more accurate way of retriving IP address.

This patch replaces nova command in 'get_instance_ip' by 'openstack'
command. Note, this nova command is the only one in devstack tree.

Change-Id: Iee0b81a994a4da5b3f4572c2e8eb30514cd43f89
Signed-off-by: Ryota MIBU <2a020678b95ddf14a5db916807d3fb3b65997655@cq.jp.nec.com>

nawawi/openstack,dtroyer/devstack,group-policy/devstack,noironetworks/devstack,noironetworks/devstack,nawawi/openstack,openstack-dev/devstack,group-policy/devstack,openstack-dev/devstack,dtroyer/devstack