Fixes#4648
Make it easier to specify IPv6 addresses in the '--add-host' option by
permitting 'host=ip' in addition to 'host:ip', and allowing square
brackets around the address.
For example:
--add-host=my-hostname:127.0.0.1
--add-host=my-hostname:::1
--add-host=my-hostname=::1
--add-host=my-hostname:[::1]
To avoid compatibility problems, the CLI will replace an '=' separator
with ':', and strip brackets, before sending the request to the API.
Signed-off-by: Rob Murray <rob.murray@docker.com>
a682b8e655