createrepo: Allow disabling SQLite database

This is an optimization for Yum. DNF does not care at all.

The behaviour is configurable, but the default depends on gather
backend, as that is what users should be using to consume the packages
from the repo.

Fixes: https://pagure.io/pungi/issue/951
Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>

tests/helpers.py

@@ -149,6 +149,7 @@ class DummyCompose(object):
         self.attempt_deliverable = mock.Mock()
         self.fail_deliverable = mock.Mock()
         self.require_deliverable = mock.Mock()
+        self.should_create_yum_database = True
 
     def setup_optional(self):
         self.all_variants['Server-optional'] = MockVariant(