Enable property expansion for insmod

Useful for dynamic kernel module location.
This permits to use init rule like:

  insmod ${persist.modules.location}/<module_name>

Change-Id: If7479bdcb4e69ea7666f52a0075c785be025c2e9
Signed-off-by: Emmanuel Berthier <emmanuel.berthier@intel.com>
(cherry picked from commit ac41230c)