Implement async OpenStack bindings using aiohttp

[denismakogon]

In order to feel the full power of async executions it is necessary to have async networking-bound operations standing behind each node type implementation, but for now, it is not. Nova, Neutron, Glance, etc. python client are built above synchronous libraries. So, each time OpenStack API being called through python clients main thread gets blocked, i.e. event loop also gets blocked.

For the certain timeframe it is necessary to implement async clients for OpenStack service like:

• novaclient
• neutron
• glance
• keystone
• cinder