Fixed attribute passing for add_interface

Server model has an `add_interface` method. This method allows attributes to be passed so you can configure options on the interface. Unfortunately it doesn't pass these options to the create_interface call. This in turn leaves `attributes` empty for `create_vm.rb#create_interface` and subsequently `create_vm.rb#create_nic_backing`. When you define a `DistributedVirtualPortgroup` as the network attribute, and `create_nic_backing` doesn't have `attributes[:datacenter]`, you will end up with a newly created StandardPortgroup instead of the correct `DistributedVirtualPortgroup` in your Backing info for the interface. To solve this you will need to pass along the `datacenter: 'name-your-dc-here'` param when you call server.add_interface, along with `type`, and `network`. 

Tested in ESX 5.5
Merge tag 'v1.24.0' into patch-1

Catching up with v1.24.0
Added GovCloud region to acceptable AWS list
[openstack] add remove header if setting directory back to private. Without it directory once public will stay like that forever.
Merge pull request #3197 from amdonov/master

Added GovCloud region to acceptable AWS list
Docker: Support for logs/top operations

In order to test this properly, responses from the mock return values
closer to what the API actually returns. Examples are from Remote API
1.18.

downcasing hash keys cannot be performed on all Docker API operations so
now it will only be done where the top element is a hash. Logs, top, and
many others will not return a hash.
Merge pull request #3199 from sulphur/master

[openstack] add remove header if setting directory back to private
Merge pull request #3202 from eLobato/docker-logs

Docker: Support for logs/top operations
Requiring fog/version
Merge pull request #3206 from plribeiro3000/edge-build

Requiring fog/version
Using `fog-xml`
Merge pull request #3181 from endzyme/patch-1

Fixed attribute passing for add_interface
Small whitespace tweak
[google|storage] Fix bug in files.get

Key was being ignored because array wasn't being saved after being
modified.
Merge pull request #3208 from icco/master

[google|storage] Fix bug in files.get
Merge pull request #3207 from plribeiro3000/using-fog-xml

Using fog/xml gem