Dependency Updates

* Dynamic Inventory Source
Template against ansible 2.3 dynamic inventory sources.
The major change is removal of `rax.py`. Most upstream scripts except
`foreman.py` has quite trivial coding style changes, or minor functional
extensions  that does not affect Tower inventory update runs.
`foreman.py`, on the other hand, went through quite a major refactoring,
but functionalities stay the same.

Major python dependency updates include apache-libcloud (1.3.0 -->
2.0.0), boto (2.45.0 --> 2.46.1) and shade (1.19.0 --> 1.20.0). Minor
python dependency updates include indirect updates via `pip-compile`,
which are determined by base dependencies.

Some minor `task.py` extensions:
 - `.ini` file for ec2 has one more field `stack_filter=False`, which
   reveals changes in `ec2.py`.
 - `.ini` file for cloudforms will catch these four options from
   `source_vars_dict` of inventory update: `'version', 'purge_actions',
   'clean_group_keys', 'nest_tags'`. These four options have always been
   available in `cloudforms.py` but `cloudforms.ini.example` has not
   mentioned them until the latest version. For consistency with upstream
   docs, we should make these fields available for tower user to customize.
 - YAML file of openstack will catch ansible options `use_hostnames`,
   `expand_hostvars` and `fail_on_errors` from `source_vars_dict` of
   inventory update as a response to issue #6075.

* Remove Rackspace support
Supports of Rackspace as both a dynamic inventory source and a cloud
credential are fully removed. Data migrations have been added to support
arbitrary credential types feature and delete rackspace inventory
sources.

Note also requirement `jsonschema` has been moved from
`requirements.txt` to `requirements.in` as a primary dependency to
reflect it's usage in `/main/fields.py`.

Connected issue: #6080.

* `pexpect` major update
`pexpect` stands at the very core of our task system and underwent a
major update from 3.1 to 4.2.1. Although verified during devel, please
still be mindful of any suspicious issues on celery side even after this
PR gets merged.

* Miscellaneous
 - requests now explicitly declared in `requirements.in` at version 2.11.1
   in response to upstream issue
 - celery: 3.1.17 -> 3.1.25
 - django-extensions: 1.7.4 -> 1.7.8
 - django-polymorphic: 0.7.2 -> 1.2
 - django-split-settings: 0.2.2 -> 0.2.5
 - django-taggit: 0.21.3 -> 0.22.1
 - irc: 15.0.4 -> 15.1.1
 - pygerduty: 0.35.1 -> 0.35.2
 - pyOpenSSL: 16.2.0 -> 17.0.0
 - python-saml: 2.2.0 -> 2.2.1
 - redbaron: 0.6.2 -> 0.6.3
 - slackclient: 1.0.2 -> 1.0.5
 - tacacs_plus: 0.1 -> 0.2
 - xmltodict: 0.10.2 -> 0.11.0
 - pip: 8.1.2 -> 9.0.1
 - setuptools: 23.0.0 -> 35.0.2
 - (requirements_ansible.in only)kombu: 3.0.35 -> 3.0.37

awx/settings/defaults.py

@@ -632,32 +632,6 @@ AD_HOC_COMMANDS = [
     'win_user',
 ]
 
-# Not possible to get list of regions without authenticating, so use this list
-# instead (based on docs from:
-# http://docs.rackspace.com/loadbalancers/api/v1.0/clb-devguide/content/Service_Access_Endpoints-d1e517.html)
-RAX_REGION_CHOICES = [
-    ('ORD', _('Chicago')),
-    ('DFW', _('Dallas/Ft. Worth')),
-    ('IAD', _('Northern Virginia')),
-    ('LON', _('London')),
-    ('SYD', _('Sydney')),
-    ('HKG', _('Hong Kong')),
-]
-
-# Inventory variable name/values for determining if host is active/enabled.
-RAX_ENABLED_VAR = 'rax_status'
-RAX_ENABLED_VALUE = 'ACTIVE'
-
-# Inventory variable name containing unique instance ID.
-RAX_INSTANCE_ID_VAR = 'rax_id'
-
-# Filter for allowed group/host names when importing inventory from Rackspace.
-# By default, filter group of one created for each instance and exclude all
-# groups without children, hosts and variables.
-RAX_GROUP_FILTER = r'^(?!instance-.+).+$'
-RAX_HOST_FILTER = r'^.+$'
-RAX_EXCLUDE_EMPTY_GROUPS = True
-
 INV_ENV_VARIABLE_BLACKLIST = ("HOME", "USER", "_", "TERM")
 
 # ----------------