Fix the empty machines

Among other things, https://whetstone.privatestorage.io/opensource/PrivateStorageio/-/merge_requests/72 shuffles around the way morph refers to machines in the deployment a little. This was not strictly necessary and I should have known better!

These changes tickle https://github.com/DBCDK/morph/issues/77 which cause morph to empty a completely empty network for the grid. Joy.

This MR updates our nixpkgs to a version with two changes:

• The incompatibility between morph >=1.3.1 and NixOS AWS support has been mitigated with a change to the nixpkgs definitions for AWS EC2 support (https://github.com/PrivateStorageio/nixpkgs/commit/b8240ab9525aaab8f8587e8aaf7be99fcca5c220)
• Morph has been upgraded to 1.4.0 which includes a fix for the bug that results in an empty network (https://github.com/PrivateStorageio/nixpkgs/compare/c54e4650cadc90152a345e070d7036cdda3aae8e..d7c46f46c3e6acfcde44bb05877fd5c9f07dfe1b)