Revert "Revert "[rackspace] adding accept headers to block_storage, cdn, compute_v2, databases, identity, load_balancers, storage""

This reverts commit f64e312e92b88e5c5459a97e02064b643facafc5.
[rackspace] fixing merge
[openstack|identity] user model tests fixes

- update_tenant expects a tenant model or a tenant_id
- update_enabled expects a boolean
[openstack|identity] cleanup the test role when no longer in use
[openstack|compute] images collection should not return nil for #all

Fog::Compute[:openstack].images.all returns nil without the patch.
The patch should bring the images collection behaviour in-line with
other collections I think.

The added test should expose the issue.
Merge pull request #1624 from rubiojr/openstack-compute-images-fixes

[openstack|compute] images collection should not return nil for #all
Typo in instantiate_vapp_template.rb

Remove typo in instantiate_vapp_template()
Merge pull request #1625 from dJason/patch-1

Typo in instantiate_vapp_template.rb
Merge pull request #1618 from rackspace/accept_fix

[Rackspace] Fixed Other Service endpoints and added accept headers
[virtualbox] Removed VirtualBox since it has many problems and the gem it's based on is no longer maintained.

Fixes #1621: Remove VirtualBox support
Merge pull request #1626 from fog/remove_virtualbox

[virtualbox] Removed VirtualBox since it has many problems and the gem it's based on is no longer maintained.
Merge pull request #1623 from bvox/openstack-identity-test-fixes

[openstack|identity] user model tests fixes