[digitalocean|compute] added some more request

- create_ssh_key
- list_ssh_keys
[digitalocean|compute] Added list_flavors mock code
[digitalocean|compute] Added list_images mock code
[digitalocean|compute] added list_servers mock code
[digitalocean|compute] added list_regions mock code
[digitalocean|compute] initialize compute service mock data
[digitalocean|compute] added create_server mock code
[digitalocean|compute] added create_ssh_key mock code
[digitalocean|compute] added destroy_server mock code
[digitalocean|compute] added get_server_details mock code
[digitalocean|compute] list_servers uses mock data
[digitalocean|compute] added list_ssh_keys mock code
[digitalocean|compute] added power_cycle_server mock code
[digitalocean|compute] added power_off_server mock code
[digitalocean|compute] added power_on_server mock code
[digitalocean|compute] added reboot_server mock code
[digitalocean|compute] added shutdown_server mock code
[digitalocean|compute] added list_ssh_keys request tests
[digitalocean|compute] mark Server.reboot test pending if mocking
[digitalocean|compute] do not run at_exit block when mocking