Use fog 1.21.0

This allows us to stop holding credentials in the .fog file and use an environment variable instead.

This includes the raw fog changes only. To use it you'll need to get a session token, by externally logging in, and set that as FOG_VCLOUD_TOKEN ENV var.
See fog/fog#2705 for further detail.

There are further changes required in other vcloud repos where they depend on fog directly before this feature can be fully adopted.

I've ran the full integration tests on vcloud-tools, net-launcher, edge-gateway, and walker and didn't see any problems.