Add tests for "Conflicts: module(name)" in MMDResolver.
The test tests installation of multiple streams of single module.
For example:
- "app:1" requires "foo:1" and "gtk:1".
- "foo:1" requires "bar:1".
- "gtk:1" requires "bar:2".
"bar:1" and "bar:2" cannot be installed in the same time and therefore
there need to be conflict defined between them.