Merge and intersect lists without using sets.

Using sets for these operations is dangerous because sets cannot contain
certain object types (such as lists) and their iteration order is
undefined.

Fixes #7596
Ensure there are no duplicates in the merged/intersected lists
Add rax_meta module

Also update rax to mirror meta value normalization from rax_meta
Don't use deprecated BaseException.message in keystone_user

fixes error "failed to parse: <attribute 'message' of 'exceptions.BaseException' objects>
TypeError: <attribute 'message' of 'exceptions.BaseException' objects> is not JSON serializable"
Fix typo in CHANGE MASTER TO syntax
Add primary group in the first user module doc example
Fix error when using os.getlogin() without a tty
Merge pull request #7632 from cdwertmann/patch-2

Don't use deprecated BaseException.message in keystone_user
Merge pull request #7635 from josef-spak/mysql-replication-typo

Fix typo in CHANGE MASTER TO syntax
Merge pull request #7638 from yanc0/primary_group_doc_user_example

Add primary group in the first user module doc example
Merge branch 'fix-7596' of https://github.com/kilburn/ansible into kilburn-fix-7596
Merge branch 'kilburn-fix-7596' into devel
Removing cruft leftover from the deprecation of include+with_items

Also cleaning up integration tests that had checks for the empty item
attribute in certain results.

Fixes #7535
made nested lists diff lengths - caused confusion

As a relatively-new user to Ansible, the Nested Loop example made me think it was looping through both lists together (`alice` would go with `clientdb`, `bob` with `employeedb`) and not actually nested. I realize now I was just being stupid, but I feel making the example lists different lengths would prevent such confusion in the future.
Fix order of merging variables for the combined cache

Fixes #7598
Merge branch 'rax-meta' of https://github.com/sivel/ansible into sivel-rax-meta
Adding the new rax_meta module to the CHANGELOG
Merge branch 'sivel-rax-meta' into devel
Merge pull request #7656 from tsemerad/patch-1

made nested lists diff lengths - caused confusion
Tweaking make_su_cmd test

Fixes #7652