The patch removes the assumption of IPv4-only addresses in the
MemcacheConnPool. The changes are around address handling.
Namely, if a server is specified with an address
[<address>]:port (port is optional), it is assumed to be an IPv6
address [1]. If an IPv6 address is specified without "[]", an exception
is raised as it is impossible to parse such addresses correctly.
For testing, memcache can be configured to listen on the link-local,
unique-local, or ::1 (equivalent to 127.0.0.1) addresses. Link-local
addresses are assigned by default to each interface and are of the form
"fe80::dead:beef". These addresses require a scope ID, which would look
like "fe80::dead:beef%eth0" (replacing eth0 with the correct interface).
Unique-local addresses are any addresses in the fc00::/7 subnet. To add
a ULA to an interface use the "ip" utility. For example:
"ip -6 address add fc01::dead:beef dev eth0". Lastly, and probably
simplest, memcache can be configured to listen on "::1". The same
address would be used in the swift configuration, e.g. "[::1]:11211".
Note: only memcached version 1.4.25 or greater supports binding to an
IPv6 address.
Fixes #1526570
[1] IPv6 host literals:
https://tools.ietf.org/html/rfc3986#section-3.2.2
Change-Id: I8408143c1d47d24e70df56a08167c529825276a2
167bb5eeb8