Consume standard OpenStack environment settings

The OpenStack client utilities consume a set of input environment
variables for things like username and auth_url, so it's very
common for OpenStack users to have such settings set in their
environment. Indeed, things like devstack also output a shell file
to be sourced to set them. Although in a playbook it's entirely
expected that variables should be used to pass in system settings
like api passwords, for ad-hoc command line usage, needing to pass
in five parameters which are almost certainly in the environment
already reduces the utility.

Grab the environment variables and inject them as default. Special care
is taken to ensure that in the case where the values are not found, the
behavior of which parameters are required is not altered.
Add common auth handling across openstack modules

Taking a page out of the ec2 config, make sure that all of the
OpenStack modules handle the inbound auth config in the same way.
The one outlier is keystone wrt auth_url.
Pass region_name to nova_keypair

Again, on things with regions, when we're configuring it, we should
actually pass it in to the compute constructor.
template Runner.module_vars['delegate_to'] to accommodate callbacks
Re-enable the ec2_eip test
Merge branch 'jsmartin-fix_eip_regression' into devel
if python >=2.7  use the option allow_no_value=True for ini_file.
Merge branch 'asg_update' of https://github.com/jsmartin/ansible into jsmartin-asg_update
Merge branch 'jsmartin-asg_update' into devel
Fixes 8362, returns stderr if No space left on device
Merge branch 'sets_v2' of https://github.com/bcoca/ansible into bcoca-sets_v2
Merge branch 'bcoca-sets_v2' into devel
Merge branch 'callback_template_delegate' of https://github.com/sergevanginderachter/ansible into sergevanginderachter-callback_template_delegate
Merge branch 'sergevanginderachter-callback_template_delegate' into devel
(A) Fix a bug in the doc generator that was clobbering the force parameter for the copy module.

(B) This is a work in progress but the idea is to have text snippets where we can respond to tickets with a bit more helpful info.
Not active just yet.
Explain ticket stubs
Update ISSUE_TEMPLATE.md

Make issue template slightly more verbose.
File common arguments should not be used in all docs pages.
Move doc fragments back into file module.
Resolve option conflict differently.