[9.20] chg: dev: Don't open route socket if we don't need it
When automatic-interface-scan is disabled, the route socket was still being opened. Add new API to connect / disconnect from the route socket only as needed.
Additionally, move the block that disables periodic interface rescans to a place where it actually have access to the configuration values. Previously, the values were being checked before the configuration was loaded.
Backport of !9122 (merged)
Edited by Ondřej Surý