When enableRootTrustAnchor is set to false, there is really no point in
initializing the root key before starting unbound.
Fixes#15605.
(cherry picked from commit bf0e745597)
Using pkgs.lib on the spine of module evaluation is problematic
because the pkgs argument depends on the result of module
evaluation. To prevent an infinite recursion, pkgs and some of the
modules are evaluated twice, which is inefficient. Using ‘with lib’
prevents this problem.
