OpenWISP Config cache invalidation and checksum mistmatch

[Federico Capoano]

In the latest version of openwisp-config, the agent complains if the downloaded config checksum does not match what it gets from openwisp.
But in the openwisp server we cache the checksum, so there are some corner cases in which the checksum cache doesn't get refreshed and the config then is not applied because the checksum downloaded is an older cached version and doesn't match the downloaded config.

If this happens, the workaround is to change something in the config of the device to update the cache.

We will have to identify all the recurring corner cases which are not handled and make sure those events always trigger a cache invalidation. Let me know if you find any.

Best regards

Federico Capoano