TRUNK-3909, backport edit_privilege fix to 1.9.x

While working on upgrading Malawi database from 1.7 to 1.9.x I ran in the problem that is described in these openmrs core tickets: TRUNK-3386 and TRUNK-3909. I just backported into 1.9.x liquibase-update-to-latest.xml the changes included here.
Once I made this small change the database upgrade completed successfully (still testing to make sure all malawi features still work).