[fix] Invalidate controller views cache when device group context changes

Same issue as org context change: bulk_invalidate_config_get_cached_checksum
was called but invalidate_controller_views_cache was not, leaving the
DeviceChecksumView cache stale for devices in the group.

Fixes #1070

Author: mn-ram

openwisp_controller/config/base/device_group.py

@@ -15,7 +15,10 @@
 from .. import settings as app_settings
 from ..signals import group_templates_changed
 from ..sortedm2m.fields import SortedManyToManyField
-from ..tasks import bulk_invalidate_config_get_cached_checksum
+from ..tasks import (
+    bulk_invalidate_config_get_cached_checksum,
+    invalidate_controller_views_cache,
+)
 from .config import TemplatesThrough
 
 
@@ -88,6 +91,7 @@ def save(
             bulk_invalidate_config_get_cached_checksum.delay(
                 {"device__group_id": str(self.id)}
             )
+            invalidate_controller_views_cache.delay(str(self.organization_id))
 
     def get_context(self):
         return deepcopy(self.context)