Fix unload plugins behavior without filelists

For packages originating outside the System repository, we don't populate the `pkg.files` when running without filelists metadata. Use RPM database as a source instead.

dnf/plugin.py

@@ -29,6 +29,7 @@
 import logging
 import operator
 import os
+import rpm
 import sys
 import traceback
 
@@ -193,13 +194,18 @@ def unload_removed_plugins(self, transaction):
 
         # check whether removed plugin file is added at the same time (upgrade of a plugin)
         for pkg in transaction.install_set:
-            erased_plugin_files.difference_update(pkg.files)
+            erased_plugin_files.difference_update(_get_files_from_newly_installed_pkg(pkg))
 
         # unload plugins that were removed in transaction
         for plugin_file in erased_plugin_files:
             self.plugins.remove(plugins[plugin_file])
 
 
+def _get_files_from_newly_installed_pkg(pkg):
+    hdr = dnf.util.first(pkg.base._ts.dbMatch('name', pkg.name))
+    return hdr[rpm.RPMTAG_FILENAMES] if hdr else []
+
+
 def _plugin_classes():
     return Plugin.__subclasses__()