In a Sculpt system based on the upcoming phone_manager, the event filter
obtains its static configuration from /config/managed/event_filter.
Without the requirement for changes at runtime, there is no need to
have the phone_manager in the loop after all.
Without this patch however, this file was always initialized with the
template gems/sculpt/event_filter/default, which was presumably used
only at boot time until the sculpt manager has produced the first
generated event-filter configuration.
This patch applies the choice of optional configs - i.e., a custom
event_filter config - to both the config/ and the initial content of
config/managed/. So in cases where the /config/managed/event_filter
remains entirely static, the latter properly reflects the choosen
variant.