init: Run vendor-specific init hooks on post-fs

* On <= lineage-16.0 vendor init props were loaded
  during load_system_props() that was called on
  post-fs. This change restores the old behavior,
  which coincidentally allows us to read files in
  /dev/block/* (and probably more) during boot time.

Change-Id: I10072797f49b34ab05a5df068d042b8c5ddc0fb6
Signed-off-by: Lucchetto <lucchetto.tie@live.com>