Remove comps groups from purely modular variants

The comps source should not return all groups when there are only
modules defined. This fixes part of the problem: non-modular packages
will not go in by default.

The second part is the comps file in the created repository. It will be
filtered to not contain any groups (because packages from there will not
be in the repo).

Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>

tests/test_initphase.py

@@ -53,6 +53,7 @@ class TestInitPhase(PungiTestCase):
         compose = DummyCompose(self.topdir, {})
         compose.has_comps = True
         compose.variants['Everything'].groups = []
+        compose.variants['Everything'].modules = []
         phase = init.InitPhase(compose)
         phase.run()