Description of problem:
On Fedora Rawhide, the mariadb module does not have the default stream set. Because there are multiple streams available for this module, DNF will not install using `dnf module install mariadb`. It will report an error instead. Since modules should be able to install using the aforementioned command, I consider this a bug.
Steps to reproduce:
1. dnf module list mariadb
Modules should have the defaults set.
If you did not set the defaults on purpose, please share the reason and confirm that explicitely.