Add a metadata handler for GCP which allows ssh login
Add a metadata handler for GCP which allows ssh login

- this needs improvements to make it more "platform native", in
  particular GCP supports multiple users and more ssh key mangement
  options.
- at present you can login as root with any platform ssh key
- add support for uts=host and ipc=host
- set the hostname from the metadata as well

Signed-off-by: Justin Cormack <af64ee19f04db9509cb02b0e470e11e5402ef9b3@docker.com>

JohnnyLeone/linuxkit,konstruktoid/linuxkit,yankcrime/linuxkit,rn/linuxkit,justincormack/linuxkit,deitch/linuxkit,linuxkit/linuxkit,konstruktoid/linuxkit,linuxkit/linuxkit,JohnnyLeone/linuxkit,justincormack/linuxkit,rn/linuxkit,konstruktoid/linuxkit,rn/linuxkit,djs55/linuxkit,djs55/linuxkit,konstruktoid/linuxkit,furious-luke/linuxkit,rn/linuxkit,justincormack/linuxkit,justincormack/tool,deitch/linuxkit,JohnnyLeone/linuxkit,justincormack/linuxkit,furious-luke/linuxkit,yankcrime/linuxkit,linuxkit/linuxkit,JohnnyLeone/linuxkit,djs55/linuxkit,yankcrime/linuxkit,djs55/linuxkit,YuPengZTE/linuxkit,konstruktoid/linuxkit,YuPengZTE/linuxkit,YuPengZTE/linuxkit,djs55/linuxkit,deitch/linuxkit,linuxkit/linuxkit,YuPengZTE/linuxkit,riyazdf/tool,YuPengZTE/linuxkit,justincormack/linuxkit,konstruktoid/linuxkit,linuxkit/linuxkit,rn/linuxkit,yankcrime/linuxkit,deitch/linuxkit,deitch/linuxkit,yankcrime/linuxkit,furious-luke/linuxkit,yankcrime/linuxkit,YuPengZTE/linuxkit,furious-luke/linuxkit,JohnnyLeone/linuxkit,davefreitag/tool,furious-luke/linuxkit,justincormack/linuxkit