Description of problem:
Fedora 28 shipped with the reviewboard:2.5 module stream as being the default stream for those packages. It has a runtime requirement on a non-default stream of django:1.6. The DNF solver is therefore treating the packages from django:1.6 as if they should suppress the RPMs it provides from the traditional RPM repository.

DNF should only treat the chained requirements this way if it is actually enabled (meaning that the reviewboard:2.5 module has been enabled on the system). Put another way, the "default" status of a module must not recurse down to its dependents automatically.

Version-Release number of selected component (if applicable):
dnf-2.7.5-12.fc28.noarch

How reproducible:
Every time

Steps to Reproduce:
1. Install Fedora 28 Server Edition
2. `dnf install python3-django`
3. `dnf install python-django-bash-completion`

Actual results:
python3-django cannot be installed:
Error: 
 Problem: conflicting requests
  - nothing provides python-django-bash-completion = 2.0.5-1.fc28 needed by python3-django-2.0.5-1.fc28.noarch


python-bash-completion comes from the django:1.6 module instead of the base RPM repo:
Installing:
 python-django-bash-completion    noarch    1.6.11.7-2.module_1595+34c51ab8     updates-modular     21 k


Expected results:
Unless the reviewboard stream has been enabled (either explicitly or by installing a package it provides), its dependencies that are themselves not explicitly listed as default streams must not impact the package selection.

It must be possible to install python3-django while the modular repos are present on the system.

Additional info:

The enablement of reviewboard:2.5 as a default module was also a mistake and we have since added policy prohibiting this in the future, but DNF must not behave poorly in situations such as this.