This reverts commit eec83d41e3e7d9ad5bc1086198d972d55bab1203.
This broke hydra evaluation because with this commit submodule values
are allowed to be paths, however the certmgr module uses `either
(submodule ...) path` in its type, meaning it already used paths for
something else which would now be interpreted as a submodule.
c7ade6844f