Cloned for OSP 8.

This seems to be caused by an IPv4-centric connection method in /usr/lib/python2.7/site-packages/swift/common/memcached.py

This seems to fix the issue:

    119     def create(self):
    120         if ']' in self.server:
    121             # deconstruct ipv6 address in brackets
    122             server_uri = self.server.strip("[").split("]")
    123             host = server_uri[0]
    124             if len(server_uri) > 1:
    125                 port = server_uri[1].strip(":")
    126             else:
    127                 port = DEFAULT_MEMCACHED_PORT
    128         elif ':' in self.server:
    129             host, port = self.server.split(':')
    130         else:
    131             host = self.server
    132             port = DEFAULT_MEMCACHED_PORT
    133         if ":" in host:
    134             sock = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
    135         else:
    136             sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    137         sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
    138         with Timeout(self._connect_timeout):
    139             sock.connect((host, int(port)))
    140         return (sock.makefile(), sock)

The upstream bug is https://bugs.launchpad.net/swift/+bug/1526570 . It has been handled in Mitaka by a series of patches:

- https://review.openstack.org/258704 Fix IPv6 handling in MemcacheConnPool.
- https://review.openstack.org/265482 fixups for ipv6 memcache_servers docs
- https://review.openstack.org/265465 Fail early if the memcache address is invalid.
- https://review.openstack.org/265501 Make _get_addr() method a function in utils.

On a quick test, they apply (almost) flawlessly to stable/liberty, so I think it would be feasible to backport them.

This  is not blocker for 8.0 GA, will be fixed in the first async.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2016-2114.html