Support IPv6 in address check lookups.

This supports IPv6 in address DNS lookups and socket bind checks. Addresses are
looked up with the system getaddrinfo(), and the v6/v4 preference of this lookup
is respected. IPv6 address literals in the config file are expected to be
bracketed in [], and the result of lookups will be bracketed as well, to support
the ZeroMQ URI format.
Unset the IPV4ONLY socket option if available.

Since IPv6 sockets support both v4 and v6 addresses, the socket option is unset
unconditionally if the parameter is available in the zmq module. The actual
decision as to which address version to use is done by the address lookup code,
which obeys the system v4/v6 preference.
Be more resilient towards missing addresses and hostname lookup failures.
Add a unit test for passing IPv6-formatted addresses to verify_socket.
IPv6 address literals should be specified without brackets in config files.
delete `salt`. the sql statements, because "conn" is  already specified
in "_get_serv" function. If specify it again, the mysql.db in
config.option is not efficacious
Import `salt.log` ASAP.

Because we NEED to make sure that any logger instance salt instantiates is using `salt.log.SaltLoggingClass`
Complement the docstring.
Remove `traceback.format_exc()` calls where not needed.
Fix for the regression pkgrepo.managed for the PPA
adding timeout option and fixing output of a failed state
Merge pull request #4539 from ranl/develop

adding timeout option and fixing output of a failed state
Merge pull request #4538 from yml/regression_pkgrepo_managed_ppa

Fix for the regression pkgrepo.managed for the PPA
Clean up makedirs wrt recent updates and fixes
Merge pull request #4535 from s0undt3ch/develop

Minor fixes
Don;t check for dig in each function, if dig is not there, don't load
Whoops :) return False, not None!
Update ubuntu.rst

The `software-properties-common` package is required to be able to do `add-apt-repository` and not the mentioned `python-software-properties`.
Merge pull request #4545 from syphernl/patch-1

Update ubuntu.rst
Merge pull request #4506 from pengyao/develop

delete `salt`. the sql statements