Verify pillar from master on minion.

In some cases, it's possible for minion to get an invalid pillar from master,
through a mostly valid reply. Check that at least it's a dict, otherwise later
code tries to do lookups in it and fails confusingly.
Add support for `SALT_CONFIG_DIR` `env` variable. Fixes #2399.
Allow the use of `SALT_CONFIG_DIR` through API access. Refs #2399.
Make sure we have a config dir setting.
Updated the troubleshooting with a nearly identical message addressing 0.17 and 0.16 compatibility between minions and masters as the one in the FAQ that was part of pull request 8505.
Replaced string lib usage with str methods
adding the ability to configure Ipv6 to the rh_ip.py module.
Merge remote-tracking branch 'upstream/develop' into develop
SUSE bug 8428 fix

Created a workaround till SUSE fix their lsb bug. Now gives the patch version in osrelease
SUSE bug 8428 fix (update)

c&p fix
Merge pull request #8630 from UtahDave/develop

Actually allow joining a domain
Fix some minor typos
Consistency change in the documentation
Merge pull request #8636 from sylvestre/develop

Fix some minor typos
Fix more typos in the documentation
Debian is not necessary a Linux. It can also be a Freebsd or HURD based
Merge pull request #8638 from sylvestre/develop

Improve the documentation
Wrap file creation in file.managed in more restrictive umask.
Merge pull request #8578 from heewa/verify_pillar_from_master

Verify pillar from master on minion.
Merge pull request #8607 from s0undt3ch/issues/2399-env-config-dir

Support SALT_CONFIG_DIR