network: remove routing policy rule from foreign rule database when it is removed

network: remove routing policy rule from foreign rule database when it is removed

Previously, When the first link configures rules, it removes all saved
rules, which were configured by networkd previously, in the foreign rule
database, but the rules themselves are still in the database.
Thus, when the second or later link configures rules, it errnously
treats the rules already exist.
This is the root of issue #11280.

This removes rules from the foreign database when they are removed.

Fixes #11280.