Currently, the Swift proxy, object, account, and container servers bind
to IPv4 address 0.0.0.0 by default. In the case of a user setting
SERVICE_IP_VERSION=6 in their local.conf file, these Swift servers still
listen on 0.0.0.0 instead of ::, which causes a ./stack.sh run to fail.
This change explicitly sets the bind_ip variable in the Swift server
config files so that the servers bind to either 0.0.0.0 (when
SERVICE_IP_VERSION != 6) or :: (when SERVICE_IP_VERSION == 6).
This patch is related to the following patch for devstack IPv6 support:
https://review.openstack.org/#/c/192329
Change-Id: Ie268c6daf5374e67ef8710a731c3af50ffdb821e
92ad152512