schema-transfomer: don't update RT list when SI init isn't done
schema-transfomer: don't update RT list when SI init isn't done

* When RoutingInstanceST are initialized, static routes are updated.
* This update trigger an update of route targets list which should not
  be updated in the case where the RI is owned by an SNAT SI and that
  latter has not been initialized yet in the reinit function.
* Prevent the schema to remove RT of SNAT's RI and so prevent to lose SNAT
  traffic temporarily when restarting schema-transformer.

Closes-Bug: #1787371

Change-Id: I135eb89310d8cb0e34de245b363cbcb571a8eab7
(cherry picked from commit 182f70500ca104b50b26bc27906939eba49e0109)

rombie/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,rombie/contrail-controller